LD(1) User Commands LD(1)

ld — link-editor for object files

ld [-32 | -64] [-a | -r] [-b] [-B direct | -B nodirect] [-B dynamic | -B static] [-B eliminate] [-B group] [-B local] [-B reduce] [-B symbolic] [-c name] [-C] [-d y | -d n] [-D token,...] [-e epsym] [-f name | -F name] [-G] [-h name] [-i] [-I name] [-l x] [-L path] [-m] [-M mapfile] [-N string] [-o outfile] [-p auditlib] [-P auditlib] [-Q y | -Q n] [-R path] [-s] [-S supportlib] [-t] [-u symname] [-V] [-Y P,dirlist] [-z absexec] [-z allextract | -z defaultextract | -z weakextract] [-z altexec64] [-z aslr[=state]] [-z assert-deflib] [-z assert-deflib=libname] [-z combreloc | -z nocombreloc] [-z defs | -z nodefs] [-z direct | -z nodirect] [-z endfiltee] [-z fatal-warnings | -z nofatal-warnings] [-z finiarray=function] [-z globalaudit] [-z groupperm | nogroupperm] [-z guidance[=id,...]] [-z help] [-z ignore | -z record] [-z initarray=function] [-z initfirst] [-z interpose] [-z lazyload | -z nolazyload] [-z ld32=arg,...] [-z ld64=arg,...] [-z loadfltr] [-z muldefs] [-z nocompstrtab] [-z nodefaultlib] [-z nodelete] [-z nodlopen] [-z nodump] [-z noldynsym] [-z nopartial] [-z noversion] [-z now] [-z origin] [-z preinitarray=function] [-z redlocsym] [-z relaxreloc] [-z rescan] [-z rescan-now] [-z rescan-start ... -z rescan-end] [-z symbolcap] [-z target=sparc|x86] [-z text | -z textwarn | -z textoff] [-z type=exec|kmod|reloc|shared] [-z verbose] [-z wrap=symbol] filename...

The link-editor, ld, combines relocatable object files by resolving symbol references to symbol definitions, together with performing relocations. ld operates in two modes, static or dynamic, as governed by the -d option. In all cases, the output of ld is left in the file a.out by default. See NOTES.

In dynamic mode, -d y, the default, relocatable object files that are provided as arguments are combined to produce an executable object file. This file is linked at execution with any shared object files that are provided as arguments. If the -G option is specified, relocatable object files are combined to produce a shared object. Without the -G option, a dynamic executable is created.

In static mode, -d n, relocatable object files that are provided as arguments are combined to produce a static executable file. If the -r option is specified, relocatable object files are combined to produce one relocatable object file. See Static Executables.

Dynamic linking is the most common model for combining relocatable objects, and the eventual creation of processes within illumos. This environment tightly couples the work of the link-editor and the runtime linker, ld.so.1(1). Both of these utilities, together with their related technologies and utilities, are extensively documented in the Linker and Libraries Guide.

If any argument is a library, ld by default searches the library exactly once at the point the library is encountered on the argument list. The library can be either a shared object or relocatable archive. See ar.h(3HEAD).

A shared object consists of an indivisible, whole unit that has been generated by a previous link-edit of one or more input files. When the link-editor processes a shared object, the entire contents of the shared object become a logical part of the resulting output file image. The shared object is not physically copied during the link-edit as its actual inclusion is deferred until process execution. This logical inclusion means that all symbol entries defined in the shared object are made available to the link-editing process. See Chapter 4, Shared Objects, in Linker and Libraries Guide.

For an archive library, ld loads only those routines that define an unresolved external reference. ld searches the symbol table of the archive library sequentially to resolve external references that can be satisfied by library members. This search is repeated until no external references can be resolved by the archive. Thus, the order of members in the library is functionally unimportant, unless multiple library members exist that define the same external symbol. Archive libraries that have interdependencies can require multiple command line definitions, or the use of one of the -z rescan options. See Archive Processing in Linker and Libraries Guide.

ld is a cross link-editor, able to link 32-bit objects or 64-bit objects, for Sparc or x86 targets. ld uses the ELF class and machine type of the first relocatable object on the command line to govern the mode in which to operate. The mixing of 32-bit objects and 64-bit objects is not permitted. Similarly, only objects of a single machine type are allowed. See the -32, -64 and -z target options, and the LD_NOEXEC_64 environment variable.

The creation of static executables is discouraged. Since a static executable is built against system archive libraries, the executable contains system implementation details. This self-containment has a number of drawbacks.

  • The executable is immune to the benefits of system updates delivered as shared objects. The executable therefore, must be rebuilt to take advantage of many system improvements.
  • The ability of the executable to run on future releases can be compromised.
  • The duplication of system implementation details negatively affects system performance.

On illumos, system archive libraries (such as libc.a) have never been provided. Without these libraries, the creation of static executables is not achievable without specialized system knowledge. However, the capability of ld to process static linking options, and the processing of archive libraries, remains.

The following options are supported.

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Creates a 32-bit, or 64-bit object.

By default, the class of the object being generated is determined from the first ELF object processed from the command line. If no objects are specified, the class is determined by the first object encountered within the first archive processed from the command line. If there are no objects or archives, the link-editor creates a 32-bit object.

The -64 option is required to create a 64-bit object solely from a mapfile.

The -32 or -64 options can also be used in the rare case of linking entirely from an archive that contains a mixture of 32 and 64-bit objects. If the first object in the archive is not the class of the object that is required to be created, then the -32 or -64 option can be used to direct the link-editor. See The 32-bit link-editor and 64-bit link-editor in Linker and Libraries Guide.

Note that for compatibility with existing Makefiles and scripts, these options may be given multiple times and may be mixed in the same invocation: the last instance wins, so that, for example, ‘ld -64 -32 -64 ...’ gives 64-bit output.

In static mode only, produces an executable object file. Undefined references are not permitted. This option is the default behavior for static mode. The -a option can not be used with the -r option. See Static Executables

In dynamic mode only, provides no special processing for dynamic executable relocations that reference symbols in shared objects. Without the -b option, the link-editor applies techniques within a dynamic executable so that the text segment can remain read-only. One technique is the creation of special position-independent relocations for references to functions that are defined in shared objects. Another technique arranges for data objects that are defined in shared objects to be copied into the memory image of an executable at runtime.

The -b option is intended for specialized dynamic objects and is not recommended for general use. Its use suppresses all specialized processing required to ensure an object's shareability, and can even prevent the relocation of 64-bit executables.

direct | nodirect
These options govern direct binding. -B direct establishes direct binding information by recording the relationship between each symbol reference together with the dependency that provides the definition. In addition, direct binding information is established between each symbol reference and an associated definition within the object being created. The runtime linker uses this information to search directly for a symbol in the associated object rather than to carry out a default symbol search.

Direct binding information can only be established to dependencies specified with the link-edit. Thus, you should use the -z defs option. Objects that wish to interpose on symbols in a direct binding environment should identify themselves as interposers with the -z interpose option. The use of -B direct enables -z lazyload for all dependencies.

The -B nodirect option prevents any direct binding to the interfaces offered by the object being created. The object being created can continue to directly bind to external interfaces by specifying the -z direct option. See Appendix D, , in Linker and Libraries Guide.

dynamic | static
Options governing library inclusion. -B dynamic is valid in dynamic mode only. These options can be specified any number of times on the command line as toggles: if the -B static option is given, no shared objects are accepted until -B dynamic is seen. See the -l option.

eliminate
Causes any global symbols, not assigned to a version definition, to be eliminated from the symbol table. Version definitions can be supplied by means of a mapfile to indicate the global symbols that should remain visible in the generated object. This option achieves the same symbol elimination as the directive that is available as part of a mapfile version definition. This option can be useful when combining versioned and non-versioned relocatable objects. See also the -B local and -B reduce options. See Defining Additional Symbols with a mapfile in Linker and Libraries Guide.

group
Establishes a shared object and its dependencies as a group. Objects within the group are bound to other members of the group at runtime. This mode is similar to adding the object to the process by using dlopen(3C) with the RTLD_GROUP mode. An object that has an explicit dependency on a object identified as a group, becomes a member of the group.

As the group must be self contained, use of the -B group option also asserts the -z defs option.

local
Causes any global symbols, not assigned to a version definition, to be reduced to local. Version definitions can be supplied by means of a mapfile to indicate the global symbols that should remain visible in the generated object. This option achieves the same symbol reduction as the auto-reduction directive that is available as part of a mapfile version definition. This option can be useful when combining versioned and non-versioned relocatable objects. See also the -B eliminate and -B reduce options. See Defining Additional Symbols with a mapfile in Linker and Libraries Guide.

reduce
When generating a relocatable object, causes the reduction of symbolic information defined by any version definitions. Version definitions can be supplied by means of a mapfile to indicate the global symbols that should remain visible in the generated object. By default, when a relocatable object is generated, version definitions are only recorded in the output image. The actual reduction of symbolic information is carried out when the object is used in the construction of a dynamic executable or shared object. The -B reduce option is applied automatically when a dynamic executable or shared object is created.

symbolic
In dynamic mode only. When building a shared object, binds references to global symbols to their definitions, if available, within the object. Normally, references to global symbols within shared objects are not bound until runtime, even if definitions are available. This model allows definitions of the same symbol in an executable or other shared object to override the object's own definition. ld issues warnings for undefined symbols unless -z defs overrides.

The -B symbolic option is intended for specialized dynamic objects and is not recommended for general use. To reduce the runtime relocation processing that is required an object, the creation of a version definition is recommended. -c name records the configuration file name for use at runtime. Configuration files can be employed to alter default search paths, provide a directory cache, together with providing alternative object dependencies. See crle(1).

Demangles C++ symbol names displayed in diagnostic messages.

y | n
When -d y, the default, is specified, ld uses dynamic linking. When -d n is specified, ld uses static linking. See Static Executables and -B dynamic | static.

token,...
Prints debugging information as specified by each token to the standard error. The special token help indicates the full list of tokens available. See in Linker and Libraries Guide.

epsym
 
epsym
Sets the entry point address for the output file to be the symbol epsym.

name
 
name
Useful only when building a shared object. Specifies that the symbol table of the shared object is used as an auxiliary filter on the symbol table of the shared object specified by name. Multiple instances of this option are allowed. This option can not be combined with the -F option. See Generating Auxiliary Filters in Linker and Libraries Guide.

name
 
name
Useful only when building a shared object. Specifies that the symbol table of the shared object is used as a filter on the symbol table of the shared object specified by name. Multiple instances of this option are allowed. This option cannot be combined with the -f option. See Generating Standard Filters in Linker and Libraries Guide.

 
In dynamic mode only, produces a shared object. Undefined symbols are allowed. See Chapter 4, Shared Objects, in Linker and Libraries Guide.

name
 
name
In dynamic mode only, when building a shared object, records name in the object's dynamic section. name is recorded in any dynamic objects that are linked with this object rather than the object's file system name. Accordingly, name is used by the runtime linker as the name of the shared object to search for at runtime. See in Linker and Libraries Guide.

Ignores LD_LIBRARY_PATH. This option is useful when an LD_LIBRARY_PATH setting is in effect to influence the runtime library search, which would interfere with the link-editing being performed.

name
 
name
When building an executable, uses name as the path name of the interpreter to be written into the program header. The default in static mode is no interpreter. In dynamic mode, the default is the name of the runtime linker, ld.so.1(1). Either case can be overridden by -I name. exec(2) loads this interpreter when the a.out is loaded, and passes control to the interpreter rather than to the a.out directly.

x
 
x
Searches a library libx.so or libx.a, the conventional names for shared object and archive libraries, respectively. In dynamic mode, unless the -B static option is in effect, ld searches each directory specified in the library search path for a libx.so or libx.a. The directory search stops at the first directory containing either. ld chooses the file ending in .so if -l x expands to two files with names of the form libx.so and libx.a. If no libx.so is found, then ld accepts libx.a. In static mode, or when the -B static option is in effect, ld selects only the file ending in .a. ld searches a library when the library is encountered, so the placement of -l is significant. See in Linker and Libraries Guide.

path
 
path
Adds path to the library search directories. ld searches for libraries first in any directories specified by the -L options and then in the standard directories. This option is useful only if the option precedes the -l options to which the -L option applies. See Directories Searched by the Link-Editor in Linker and Libraries Guide.

The environment variable LD_LIBRARY_PATH can be used to supplement the library search path, however the -L option is recommended, as the environment variable is also interpreted by the runtime environment. See LD_LIBRARY_PATH under ENVIRONMENT.

Produces a memory map or listing of the input/output sections, together with any non-fatal multiply-defined symbols, on the standard output.

mapfile
Reads mapfile as a text file of directives to ld. This option can be specified multiple times. If mapfile is a directory, then all regular files, as defined by stat(2), within the directory are processed. See Chapter 9, , in Linker and Libraries Guide. Example mapfiles are provided in /usr/lib/ld. See FILES.

string
This option causes a DT_NEEDED entry to be added to the .dynamic section of the object being built. The value of the DT_NEEDED string is the string that is specified on the command line. This option is position dependent, and the DT_NEEDED .dynamic entry is relative to the other dynamic dependencies discovered on the link-edit line. This option is useful for specifying dependencies within device driver relocatable objects when combined with the -d y and -r options.

outfile
 
outfile
Produces an output object file that is named outfile. The name of the default object file is a.out.

auditlib
Identifies an audit library, auditlib. This audit library is used to audit the object being created at runtime. A shared object identified as requiring auditing with the -p option, has this requirement inherited by any object that specifies the shared object as a dependency. See the -P option. See Runtime Linker Auditing Interface in Linker and Libraries Guide.

auditlib
Identifies an audit library, auditlib. This audit library is used to audit the dependencies of the object being created at runtime. Dependency auditing can also be inherited from dependencies that are identified as requiring auditing. See the -p and -z globalaudit options. See Runtime Linker Auditing Interface in Linker and Libraries Guide.

y | n
Under -Q y, an string is added to the .comment section of the output file. This string identifies the version of the ld used to create the file. This results in multiple ld idents when there have been multiple linking steps, such as when using ld -r. This identification is identical with the default action of the cc(1) command. -Q n suppresses version identification. .comment sections can be manipulated by the mcs(1) utility.

 
Combines relocatable object files to produce one relocatable object file. ld does not complain about unresolved references. This option cannot be used with the -a option.

path
 
path
A colon-separated list of directories used to specify library search directories to the runtime linker. If present and not NULL, the path is recorded in the output object file and passed to the runtime linker. Multiple instances of this option are concatenated together with each path separated by a colon. See Directories Searched by the Runtime Linker in Linker and Libraries Guide.

The use of a runpath within an associated object is preferable to setting global search paths such as through the LD_LIBRARY_PATH environment variable. Only the runpaths that are necessary to find the objects dependencies should be recorded. ldd(1) can also be used to discover unused runpaths in dynamic objects, when used with the -U option.

Various tokens can also be supplied with a runpath that provide a flexible means of identifying system capabilities or an objects location. See Appendix C, , in Linker and Libraries Guide. The $ORIGIN token is especially useful in allowing dynamic objects to be relocated to different locations in the file system.

 
Strips symbolic information from the output file. Any debugging information, that is, , , and sections, and their associated relocation entries are removed. Except for relocatable files, a symbol table SHT_SYMTAB and its associated string table section are not created in the output object file. The elimination of a SHT_SYMTAB symbol table can reduce the .stab* debugging information that is generated using the compiler driver's -g option. See the -z redlocsym and -z noldynsym options.

supportlib
The shared object supportlib is loaded with ld and given information regarding the linking process. Shared objects that are defined by using the -S option can also be supplied using the SGS_SUPPORT environment variable. See Link-Editor Support Interface in Linker and Libraries Guide.

Turns off the warning for multiply-defined symbols that have different sizes or different alignments.

symname
 
symname
Enters symname as an undefined symbol in the symbol table. This option is useful for loading entirely from an archive library. In this instance, an unresolved reference is needed to force the loading of the first routine. The placement of this option on the command line is significant. This option must be placed before the library that defines the symbol. See Defining Additional Symbols with the u option in Linker and Libraries Guide.

 
Outputs a message giving information about the version of ld being used.

P,dirlist
Changes the default directories used for finding libraries. dirlist is a colon-separated path list.

absexec
Useful only when building a dynamic executable. Specifies that references to external absolute symbols should be resolved immediately instead of being left for resolution at runtime. In very specialized circumstances, this option removes text relocations that can result in excessive swap space demands by an executable.

allextract | defaultextract | weakextract
 
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Alters the extraction criteria of objects from any archives that follow. By default, archive members are extracted to satisfy undefined references and to promote tentative definitions with data definitions. Weak symbol references do not trigger extraction. Under the -z allextract or --whole-archive options, all archive members are extracted from the archive. Under -z weakextract, weak references trigger archive extraction. The -z defaultextract or --no-whole-archive options provide a means of returning to the default following use of the former extract options. See Archive Processing in Linker and Libraries Guide.

altexec64
Execute the 64-bit ld. The creation of very large 32-bit objects can exhaust the virtual memory that is available to the 32-bit ld. The -z altexec64 option can be used to force the use of the associated 64-bit ld. The 64-bit ld provides a larger virtual address space for building 32-bit objects. See The 32-bit link-editor and 64-bit link-editor in Linker and Libraries Guide.

aslr[=state]
Specify whether the executable's address space should be randomized on execution. If state is enabled, randomization will always occur when this executable is run (regardless of inherited settings). If state is disabled, randomization will never occur when this executable is run. If state is omitted, ASLR is enabled. An executable that should simply use the settings inherited from its environment should not use this flag at all.

combreloc | nocombreloc
By default, ld combines multiple relocation sections when building executables or shared objects. This section combination differs from relocatable objects, in which relocation sections are maintained in a one-to-one relationship with the sections to which the relocations must be applied. The -z nocombreloc option disables this merging of relocation sections, and preserves the one-to-one relationship found in the original relocatable objects.

ld sorts the entries of data relocation sections by their symbol reference. This sorting reduces runtime symbol lookup. When multiple relocation sections are combined, this sorting produces the least possible relocation overhead when objects are loaded into memory, and speeds the runtime loading of dynamic objects.

Historically, the individual relocation sections were carried over to any executable or shared object, and the -z combreloc option was required to enable the relocation section merging previously described. Relocation section merging is now the default. The -z combreloc option is still accepted for the benefit of old build environments, but the option is unnecessary, and has no effect.

assert-deflib
 
assert-deflib=libname
Enables warnings that check the location of where libraries passed in with -l are found. If the link-editor finds a library on its default search path it will emit a warning. This warning can be made fatal in conjunction with the option -z fatal-warnings. Passing libname white lists a library from this check. The library must be the full name of the library, e.g. libc.so. To white list multiple libraries, the -z assert-deflib=libname option can be repeated multiple times. This option is useful when trying to build self-contained objects where a referenced library might exist in the default system library path and in alternate paths specified by -L, but you only want the alternate paths to be used.

defs | nodefs
 
The -z defs option and the --no-undefined option force a fatal error if any undefined symbols remain at the end of the link. This mode is the default when an executable is built. For historic reasons, this mode is the default when building a shared object. Use of the -z defs option is recommended, as this mode assures the object being built is self-contained. A self-contained object has all symbolic references resolved internally, or to the object's immediate dependencies.

The -z nodefs option allows undefined symbols. For historic reasons, this mode is the default when a shared object is built. When used with executables, the behavior of references to such undefined symbols is unspecified. Use of the -z nodefs option is not recommended.

direct | nodirect
Enables or disables direct binding to any dependencies that follow on the command line. These options allow finer control over direct binding than the global counterpart -B direct. The -z direct option also differs from the -B direct option in the following areas. Direct binding information is not established between a symbol reference and an associated definition within the object being created. Lazy loading is not enabled.

endfiltee
Marks a filtee so that when processed by a filter, the filtee terminates any further filtee searches by the filter. See in Linker and Libraries Guide.

fatal-warnings | nofatal-warnings
 
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Controls the behavior of warnings emitted from the link-editor. Setting -z fatal-warnings promotes warnings emitted by the link-editor to fatal errors that will cause the link-editor to fail before linking. -z nofatal-warnings instead demotes these warnings such that they will not cause the link-editor to exit prematurely.

finiarray=function
Appends an entry to the .fini_array section of the object being built. If no .fini_array section is present, a section is created. The new entry is initialized to point to function. See Initialization and Termination Sections in Linker and Libraries Guide.

globalaudit
This option supplements an audit library definition that has been recorded with the -P option. This option is only meaningful when building a dynamic executable. Audit libraries that are defined within an object with the -P option typically allow for the auditing of the immediate dependencies of the object. The -z globalaudit promotes the auditor to a global auditor, thus allowing the auditing of all dependencies. See in Linker and Libraries Guide.

An auditor established with the -P option and the -z globalaudit option, is equivalent to the auditor being established with the LD_AUDIT environment variable. See ld.so.1(1).

groupperm | nogroupperm
Assigns, or deassigns each dependency that follows to a unique group. The assignment of a dependency to a group has the same effect as if the dependency had been built using the -B group option.

guidance[=id,...]
Give messages suggesting link-editor features that could improve the resulting dynamic object. Specific classes of suggestion can be silenced by specifying an optional comma separated list of guidance identifiers. The current classes of suggestion provided are:
Enable use of direct binding
Suggests that -z direct or -B direct be present prior to any specified dependency. This allows predictable symbol binding at runtime. Can be disabled with -z guidance=nodirect
Enable lazy dependency loading
Suggests that -z lazyload be present prior to any specified dependency. This allows the dynamic object to be loaded more quickly. Can be disabled with -z guidance=nolazyload
Shared objects should define all their dependencies.
Suggests that -z defs be specified on the link-editor command line. Shared objects that explicitly state all their dependencies behave more predictably when used. Can be be disabled with -z guidance=nodefs
Version 2 mapfile syntax
Suggests that any specified mapfiles use the more readable version 2 syntax. Can be disabled with -z guidance=nomapfile
Read-only text segment
Should any runtime relocations within the text segment exist, suggests that the object be compiled with position independent code (PIC). Keeping large allocatable sections read-only allows them to be shared between processes using a given shared object. Can be disabled with -z guidance=notext
Suggests that any dependency not referenced by the resulting dynamic object be removed from the link-editor command line. Can be disabled with -z guidance=nounused
Global data in shared libraries built with mapfiles have size assertions
Suggests that any global data in a library built with a mapfile asserts the size of that global data for ABI stability purposes. Can be disabled with -z guidance=noasserts

help
 
Print a summary of the command line options on the standard output and exit.

ignore | record
Ignores, or records, dynamic dependencies that are not referenced as part of the link-edit. Ignores, or records, unreferenced ELF sections from the relocatable objects that are read as part of the link-edit. By default, -z record is in effect.

If an ELF section is ignored, the section is eliminated from the output file being generated. A section is ignored when three conditions are true. The eliminated section must contribute to an allocatable segment. The eliminated section must provide no global symbols. No other section from any object that contributes to the link-edit, must reference an eliminated section.

initarray=function
Appends an entry to the .init_array section of the object being built. If no .init_array section is present, a section is created. The new entry is initialized to point to function. See Initialization and Termination Sections in Linker and Libraries Guide.

initfirst
Marks the object so that its runtime initialization occurs before the runtime initialization of any other objects brought into the process at the same time. In addition, the object runtime finalization occurs after the runtime finalization of any other objects removed from the process at the same time. This option is only meaningful when building a shared object.

interpose
Marks the object as an interposer. At runtime, an object is identified as an explicit interposer if the object has been tagged using the -z interpose option. An explicit interposer is also established when an object is loaded using the LD_PRELOAD environment variable. Implicit interposition can occur because of the load order of objects, however, this implicit interposition is unknown to the runtime linker. Explicit interposition can ensure that interposition takes place regardless of the order in which objects are loaded. Explicit interposition also ensures that the runtime linker searches for symbols in any explicit interposers when direct bindings are in effect.

lazyload | nolazyload
Enables or disables the marking of dynamic dependencies to be lazily loaded. Dynamic dependencies which are marked Cm lazyload are not loaded at initial process start-up. These dependencies are delayed until the first binding to the object is made. Note: Lazy loading requires the correct declaration of dependencies, together with associated runpaths for each dynamic object used within a process. See in Linker and Libraries Guide.

ld32=arg,...
 
ld64=arg,...
The class of the link-editor is affected by the class of the output file being created and by the capabilities of the underlying operating system. The -z ld32 | ld64 options provide a means of defining any link-editor argument. The defined argument is only interpreted, respectively, by the 32-bit class or 64-bit class of the link-editor.

For example, support libraries are class specific, so the correct class of support library can be ensured using:

ld ... -z ld32=-Saudit32.so.1 -z ld64=-Saudit64.so.1 ...

The class of link-editor that is invoked is determined from the ELF class of the first relocatable file that is seen on the command line. This determination is carried out to any -z ld32 | ld64 processing.

loadfltr
Marks a filter to indicate that filtees must be processed immediately at runtime. Normally, filter processing is delayed until a symbol reference is bound to the filter. The runtime processing of an object that contains this flag mimics that which occurs if the LD_LOADFLTR environment variable is in effect. See the ld.so.1(1).

muldefs
 
Allows multiple symbol definitions. By default, multiple symbol definitions that occur between relocatable objects result in a fatal error condition. This option, suppresses the error condition, allowing the first symbol definition to be taken.

nocompstrtab
Disables the compression of ELF string tables. By default, string compression is applied to SHT_STRTAB sections, and to SHT_PROGBITS sections that have their SHF_MERGE and SHF_STRINGS section flags set.

nodefaultlib
Marks the object so that the runtime default library search path, used after any LD_LIBRARY_PATH or runpaths, is ignored. This option implies that all dependencies of the object can be satisfied from its runpath.

nodelete
Marks the object as non-deletable at runtime. This mode is similar to adding the object to the process by using dlopen(3C) with the RTLD_NODELETE mode.

nodlopen
Marks the object as not available to dlopen(3C), either as the object specified by the dlopen(3C), or as any form of dependency required by the object specified by the dlopen(3C). This option is only meaningful when building a shared object.

nodump
Marks the object as not available to dldump(3C).

noldynsym
Prevents the inclusion of a .SUNW_ldynsym section in dynamic executables or sharable libraries. The .SUNW_ldynsym section augments the section by providing symbols for local functions. Local function symbols allow debuggers to display local function names in stack traces from stripped programs. Similarly, dladdr(3C) is able to supply more accurate results.

The -z noldynsym option also prevents the inclusion of the two symbol sort sections that are related to the .SUNW_ldynsym section. The .SUNW_dynsymsort section provides sorted access to regular function and variable symbols. The .SUNW_dyntlssort section provides sorted access to thread local storage (TLS) variable symbols.

The .SUNW_ldynsym, .SUNW_dynsymsort, and .SUNW_dyntlssort sections, which becomes part of the allocable text segment of the resulting file, cannot be removed by strip(1). Therefore, the -z noldynsym option is the only way to prevent their inclusion. See the -s and -z redlocsym options.

nopartial
Partially initialized symbols, that are defined within relocatable object files, are expanded in the output file being generated.

noversion
Does not record any versioning sections. Any version sections or associated .dynamic section entries are not generated in the output image.

now
Marks the object as requiring non-lazy runtime binding. This mode is similar to adding the object to the process by using dlopen(3C) with the RTLD_NOW mode. This mode is also similar to having the LD_BIND_NOW environment variable in effect. See ld.so.1(1).

origin
Marks the object as requiring immediate $ORIGIN processing at runtime. This option is only maintained for historic compatibility, as the runtime analysis of objects to provide for $ORIGIN processing is now default.

preinitarray=function
Appends an entry to the .preinitarray section of the object being built. If no .preinitarray section is present, a section is created. The new entry is initialized to point to function. See Initialization and Termination Sections in Linker and Libraries Guide.

redlocsym
Eliminates all local symbols except for the SECT symbols from the symbol table SHT_SYMTAB. All relocations that refer to local symbols are updated to refer to the corresponding SECT symbol. This option allows specialized objects to greatly reduce their symbol table sizes. Eliminated local symbols can reduce the debugging information that is generated using the compiler driver's -g option. See the -s and -z noldynsym options.

relaxreloc
ld normally issues a fatal error upon encountering a relocation using a symbol that references an eliminated COMDAT section. If -z relaxreloc is enabled, ld instead redirects such relocations to the equivalent symbol in the COMDAT section that was kept. -z relaxreloc is a specialized option, mainly of interest to compiler authors, and is not intended for general use.

rescan-now
 
rescan
These options rescan the archive files that are provided to the link-edit. By default, archives are processed once as the archives appear on the command line. Archives are traditionally specified at the end of the command line so that their symbol definitions resolve any preceding references. However, specifying archives multiple times to satisfy their own interdependencies can be necessary.

-z rescan-now is a positional option, and is processed by the link-editor immediately when encountered on the command line. All archives seen on the command line up to that point are immediately reprocessed in an attempt to locate additional archive members that resolve symbol references. This archive rescanning is repeated until a pass over the archives occurs in which no new members are extracted.

-z rescan is a position independent option. The link-editor defers the rescan operation until after it has processed the entire command line, and then initiates a final rescan operation over all archives seen on the command line. The -z rescan operation can interact incorrectly with objects that contain initialization (.init) or finalization (.fini) sections, preventing the code in those sections from running. For this reason, -z rescan is deprecated, and use of -z rescan-now is advised.

rescan-start ... -z rescan-end
 
... --end-group
 
... -)
Defines an archive rescan group. This is a positional construct, and is processed by the link-editor immediately upon encountering the closing delimiter option. Archives found within the group delimiter options are reprocessed as a group in an attempt to locate additional archive members that resolve symbol references. This archive rescanning is repeated until a pass over the archives occurs in which no new members are extracted. Archive rescan groups cannot be nested.

symbolcap
Specifies that a relocatable object that defines object capabilities should have those converted to symbol capabilities. A relocatable object that does not have any object capabilities will ignore this option.

Symbol capabilities provide a means for multiple implementations of a function to co-exist and have one picked at runtime based upon the hardware capabilities of the system. When -z symbolcap is invoked, all global functions are converted into local functions that have the corresponding capability name appended to them and an undefined symbol with the original name left in the resulting relocatable object. At runtime, the global symbol will be bound to the corresponding implementation that is appropriate based on the capabilities of the system.

target=sparc|x86
Specifies the machine type for the output object. Supported targets are sparc and x86. The 32-bit machine type for the specified target is used unless the -64 option is also present, in which case the corresponding 64-bit machine type is used. By default, the machine type of the object being generated is determined from the first ELF object processed from the command line. If no objects are specified, the machine type is determined by the first object encountered within the first archive processed from the command line. If there are no objects or archives, the link-editor assumes the native machine. This option is useful when creating an object directly with ld whose input is solely from a mapfile. See the -M option. It can also be useful in the rare case of linking entirely from an archive that contains objects of different machine types for which the first object is not of the desired machine type. See The 32-bit link-editor and 64-bit link-editor in Linker and Libraries Guide.

Note that for compatibility with existing Makefiles and scripts, these options may be given multiple times and may be mixed in the same invocation: the last instance wins, so that, for example, ‘ld -z target=sparc -z target=x86 ...’ gives a machine type of ‘x86’.

text
In dynamic mode only, forces a fatal error if any relocations against non-writable, allocatable sections remain. For historic reasons, this mode is not the default when building an executable or shared object. However, its use is recommended to ensure that the text segment of the dynamic object being built is shareable between multiple running processes. A shared text segment incurs the least relocation overhead when loaded into memory. See in Linker and Libraries Guide.

textoff
In dynamic mode only, allows relocations against all allocatable sections, including non-writable ones. This mode is the default when building a shared object.

textwarn
In dynamic mode only, lists a warning if any relocations against non-writable, allocatable sections remain. This mode is the default when building an executable.

-z type=exec|||
Specifies the type of object to create.
exec
Dynamic executable
reloc
Relocatable object
shared
Dynamic shared object
kmod
illumos kernel module

verbose
This option provides additional warning diagnostics during a link-edit. Presently, this option conveys suspicious use of displacement relocations. This option also conveys the restricted use of static TLS relocations when building shared objects. In future, this option might be enhanced to provide additional diagnostics that are deemed too noisy to be generated by default.

wrap=symbol
 
=symbol
 
=symbol
Rename undefined references to symbol in order to allow wrapper code to be linked into the output object without having to modify source code. When -z wrap is specified, all undefined references to symbol are modified to reference __wrap_symbol, and all references to __real_symbol are modified to reference symbol. The user is expected to provide an object containing the __wrap_symbol function. This wrapper function can call __real_symbol in order to reference the actual function being wrapped.

The following is an example of a wrapper for the malloc(3C) function:

void *
__wrap_malloc(size_t c)
{
    (void) printf("malloc called with %zu\n", c);
    return (__real_malloc(c));
}

If you link other code with this file using -z wrap=malloc to compile all the objects, then all calls to malloc will call the function instead. The call to will call the real malloc function.

The real and wrapped functions should be maintained in separate source files. Otherwise, the compiler or assembler may resolve the call instead of leaving that operation for the link-editor to carry out, and prevent the wrap from occurring.

An alternative link-editor path name. ld executes, and passes control to this alternative link-editor. This environment variable provides a generic means of overriding the default link-editor that is called from the various compiler drivers. See the -z altexec64 option.
A list of directories in which to search for the libraries specified using the -l option. Multiple directories are separated by a colon. In the most general case, this environment variable contains two directory lists separated by a semicolon:

dirlist1;dirlist2

If ld is called with any number of occurrences of -L, as in:

ld ... -Lpath1 ... -Lpathn ...

then the search path ordering is:

dirlist1 path1 ... pathn dirlist2 LIBPATH

When the list of directories does not contain a semicolon, the list is interpreted as dirlist2.

The LD_LIBRARY_PATH environment variable also affects the runtime linkers search for dynamic dependencies.

This environment variable can be specified with a _32 or _64 suffix. This makes the environment variable specific, respectively, to 32-bit or 64-bit processes and overrides any non-suffixed version of the environment variable that is in effect.

Suppresses the automatic execution of the 64-bit link-editor. By default, the link-editor executes the 64-bit version when the ELF class of the first relocatable file identifies a 64-bit object. The 64-bit image that a 32-bit link-editor can create, has some limitations. However, some link-edits might find the use of the 32-bit link-editor faster.
A default set of options to ld. LD_OPTIONS is interpreted by ld just as though its value had been placed on the command line, immediately following the name used to invoke ld, as in:

ld $LD_OPTIONS ... other-arguments ...
An alternative mechanism for specifying a runpath to the link-editor. See the -R option. If both LD_RUN_PATH and the -R option are specified, -R supersedes.
Provides a colon-separated list of shared objects that are loaded with the link-editor and given information regarding the linking process. This environment variable can be specified with a _32 or _64 suffix. This makes the environment variable specific, respectively, to the 32-bit or 64-bit class of ld and overrides any non-suffixed version of the environment variable that is in effect. See the -S option.

Notice that environment variable-names that begin with the characters ‘LD_’ are reserved for possible future enhancements to ld and ld.so.1(1).

libx.so
shared object libraries.
libx.a
archive libraries.
a.out
default output file.
For 32-bit libraries, the default search path is /usr/ccs/lib, followed by /lib, and finally /usr/lib. For 64-bit libraries, the default search path is /lib/64, followed by /usr/lib/64.
/usr/lib/ld
A directory containing several mapfiles that can be used during link-editing. These mapfiles provide various capabilities, such as defining memory layouts, aligning bss, and defining non-executable stacks.

The command line interface of ld is Committed. The output of ld is Committed.

as(1), crle(1), gprof(1), ld.so.1(1), ldd(1), mcs(1), pvs(1), strip(1), exec(2), stat(2), dladdr(3C), dldump(3C), dlopen(3C), malloc(3C), elf(3ELF), ar.h(3HEAD), a.out(5), attributes(7)

Linker and Libraries Guide.

Default options applied by ld are maintained for historic reasons. In today's programming environment, where dynamic objects dominate, alternative defaults would often make more sense. However, historic defaults must be maintained to ensure compatibility with existing program development environments. Historic defaults are called out wherever possible in this manual. For a description of the current recommended options, see Appendix A, Link-Editor Quick Reference, in Linker and Libraries Guide.

If the file being created by ld already exists, the file is unlinked after all input files have been processed. A new file with the specified name is then created. This allows ld to create a new version of the file, while simultaneously allowing existing processes that are accessing the old file contents to continue running. If the old file has no other links, the disk space of the removed file is freed when the last process referencing the file terminates.

The behavior of ld when the file being created already exists was changed with SXCE build 43. In older versions, the existing file was rewritten in place, an approach with the potential to corrupt any running processes that is using the file. This change has an implication for output files that have multiple hard links in the file system. Previously, all links would remain intact, with all links accessing the new file contents. The new ld behavior such links, with the result that only the specified output file name references the new file. All the other links continue to reference the old file. To ensure consistent behavior, applications that rely on multiple hard links to linker output files should explicitly remove and relink the other file names.

January 15, 2024 OmniOS