diff options
Diffstat (limited to 'ld/ld.texinfo')
| -rw-r--r-- | ld/ld.texinfo | 200 |
1 files changed, 32 insertions, 168 deletions
diff --git a/ld/ld.texinfo b/ld/ld.texinfo index a5430a1..d71c086 100644 --- a/ld/ld.texinfo +++ b/ld/ld.texinfo @@ -163,19 +163,19 @@ line: @c FIXME! -relax only avail h8/300, i960. Conditionals screwed in examples. @smallexample -ld [-o @var{output} ] @var{objfile}@dots{} +ld [ -o @var{output} ] @var{objfile}@dots{} [ -A@var{architecture} ] [ -b @var{input-format} ] [ -Bstatic ] [ -c @var{MRI-commandfile} ] [ -d | -dc | -dp ] [ -defsym @var{symbol}=@var{expression} ] [ -e @var{entry} ] [ -F ] [ -F @var{format} ] - [ -format @var{input-format} ] [ -g ] [ -G @var{size} ] [ -i ] - [ -l@var{ar} ] [ -L@var{searchdir} ] [ -M ] [ -Map @var{mapfile} ] + [ -format @var{input-format} ] [ -g ] [ -G @var{size} ] [ --help ] [ -i ] + [ -l@var{archive} ] [ -L@var{searchdir} ] [ -M ] [ -Map @var{mapfile} ] [ -m @var{emulation} ] [ -N | -n ] [ -noinhibit-exec ] [ -oformat @var{output-format} ] [ -R @var{filename} ] [ -relax ] [ -r | -Ur ] [ -S ] [ -s ] [ -T @var{commandfile} ] [ -Ttext @var{textorg} ] [ -Tdata @var{dataorg} ] - [ -Tbss @var{bssorg} ] [ -t ] [ -u @var{sym}] [-V] [-v] [ -X ] [-x ] - [ -y@var{symbol} ] + [ -Tbss @var{bssorg} ] [ -t ] [ -u @var{symbol}] [-V] [-v] [ --version ] + [ -y@var{symbol} ] [ -X ] [-x ] @end smallexample This plethora of command-line options may seem intimidating, but in @@ -358,17 +358,26 @@ Ignored. Provided for compatibility with other tools. Set the maximum size of objects to be optimized using the GP register to @var{size} under MIPS ECOFF. Ignored for other object file formats. +@item --help +@kindex --help +@cindex help +@cindex usage +Print a summary of the command-line options on the standard output and exit. +This option and @samp{--version} begin with two dashes instead of one +for compatibility with other GNU programs. The other options start with +only one dash for compatibility with other linkers. + @kindex -i @cindex incremental link @item -i Perform an incremental link (same as option @samp{-r}). @cindex archive files, from cmd line -@kindex -l@var{ar} +@kindex -l@var{archive} @item -l@var{ar} -Add archive file @var{ar} to the list of files to link. This +Add archive file @var{archive} to the list of files to link. This option may be used any number of times. @code{ld} will search its -path-list for occurrences of @code{lib@var{ar}.a} for every @var{ar} +path-list for occurrences of @code{lib@var{ar}.a} for every @var{archive} specified. @cindex search directory, from cmd line @@ -519,16 +528,12 @@ for compatibility with other linkers, you may omit the leading @itemx -T@var{commandfile} @kindex -T @var{script} @cindex script files -Read link commands from the file -@var{commandfile}. These commands completely override @code{ld}'s -default link format (rather than adding to it); @var{commandfile} must -specify everything necessary to describe the target format. -@xref{Commands}. -If @var{commandfile} does not exist, @code{ld} looks for it in the directories -specified by any @samp{-L} options. - -You may also include a script of link commands directly in the command -line by bracketing it between @samp{@{} and @samp{@}}. +Read link commands from the file @var{commandfile}. These commands +completely override @code{ld}'s default link format (rather than adding +to it); @var{commandfile} must specify everything necessary to describe +the target format. @xref{Commands}. If @var{commandfile} does not +exist, @code{ld} looks for it in the directories specified by any +preceding @samp{-L} options. Multiple @samp{-T} options accumulate. @item -t @kindex -t @@ -536,10 +541,10 @@ line by bracketing it between @samp{@{} and @samp{@}}. @cindex input files, displaying Print the names of the input files as @code{ld} processes them. -@item -u @var{sym} -@kindex -u @var{sym} +@item -u @var{symbol} +@kindex -u @var{symbol} @cindex undefined symbol -Force @var{sym} to be entered in the output file as an undefined symbol. +Force @var{symbol} to be entered in the output file as an undefined symbol. Doing this may, for example, trigger linking of additional modules from standard libraries. @samp{-u} may be repeated with different option arguments to enter additional undefined symbols. @@ -558,13 +563,16 @@ turn serve as input to @code{ld}. When linking C++ programs, @samp{-Ur} @kindex -V @cindex version Display the version number for @code{ld} and list the supported emulations. -Print which input files can and can not be opened. +Display which input files can and can not be opened. @item -v @kindex -v @cindex version Display the version number for @code{ld}. -Print which input files can and can not be opened. + +@item --version +@kindex --version +Display the version number for @code{ld} and exit. @item -X @kindex -X @@ -638,9 +646,6 @@ an ordinary file. If the linker opens a file which it cannot recognize as a supported object or archive format, it tries to interpret the file as a command file. -You can also include a script directly on the @code{ld} command line, -delimited by the characters @samp{@{} and @samp{@}}. - @menu * Scripts:: Linker Scripts * Expressions:: Expressions @@ -2008,148 +2013,7 @@ conversion and during output. @xref{BFD information loss}. @node BFD outline @section How it works: an outline of BFD @cindex opening object files -When an object file is opened, BFD subroutines automatically -determine the format of the input object file, and build a descriptor in -memory with pointers to routines that will be used to access elements of -the object file's data structures. - -As different information from the the object files is required, -BFD reads from different sections of the file and processes them. -For example, a very common operation for the linker is processing symbol -tables. Each BFD back end provides a routine for converting -between the object file's representation of symbols and an internal -canonical format. When the linker asks for the symbol table of an object -file, it calls through the memory pointer to the BFD -back end routine which reads and converts the table into a canonical -form. The linker then operates upon the common form. When the link is -finished and the linker writes the symbol table of the output file, -another BFD back end routine is called which takes the newly -created symbol table and converts it into the chosen output format. - -@node BFD information loss -@section Information Loss -@emph{Information can be lost during output.} The output formats -supported by BFD do not provide identical facilities, and -information which may be described in one form has nowhere to go in -another format. One example of this is alignment information in -@code{b.out}. There is nowhere in an @code{a.out} format file to store -alignment information on the contained data, so when a file is linked -from @code{b.out} and an @code{a.out} image is produced, alignment -information will not propagate to the output file. (The linker will -still use the alignment information internally, so the link is performed -correctly). - -Another example is COFF section names. COFF files may contain an -unlimited number of sections, each one with a textual section name. If -the target of the link is a format which does not have many sections (e.g., -@code{a.out}) or has sections without names (e.g., the Oasys format) the -link cannot be done simply. You can circumvent this problem by -describing the desired input-to-output section mapping with the command -language. - -@emph{Information can be lost during canonicalization.} The BFD -internal canonical form of the external formats is not exhaustive; there -are structures in input formats for which there is no direct -representation internally. This means that the BFD back ends -cannot maintain all possible data richness through the transformation -between external to internal and back to external formats. - -This limitation is only a problem when using the linker to read one -format and write another. Each BFD back end is responsible for -maintaining as much data as possible, and the internal BFD -canonical form has structures which are opaque to the BFD core, -and exported only to the back ends. When a file is read in one format, -the canonical form is generated for BFD and the linker. At the -same time, the back end saves away any information which would otherwise -be lost. If the data is then written back in the same format, the back -end routine will be able to use the canonical form provided by the -BFD core as well as the information it prepared earlier. Since -there is a great deal of commonality between back ends, -there is no information lost when -linking big endian COFF to little endian COFF, or from @code{a.out} to -@code{b.out}. When a mixture of formats is linked, the information is -only lost from the files whose format differs from the destination. - -@node Mechanism -@section Mechanism -The greatest potential for loss of information occurs when there is the least -overlap between the information provided by the source format, that -stored by the canonical format, and that needed by the -destination format. A brief description of the canonical form may help -you understand which kinds of data you can count on preserving across -conversions. -@cindex BFD canonical format -@cindex internal object-file format - -@table @emph -@item files -Information on target machine architecture, particular implementation, -and format type are stored on a per-file basis. Other information -includes a demand pagable bit and a write protected bit. -Information like Unix magic numbers is not stored here---only the magic -numbers' meaning, so a @code{ZMAGIC} file would have both the demand pagable -bit and the write protected text bit set. - -The byte order of the target is stored on a per-file basis, so that big- -and little-endian object files may be linked with one another. - -@item sections -Each section in the input file contains the name of the section, the -original address in the object file, various options, size and alignment -information and pointers into other BFD data structures. - -@item symbols -Each symbol contains a pointer to the object file which originally -defined it, its name, its value, and various option bits. When a -BFD back end reads in a symbol table, the back end relocates all -symbols to make them relative to the base of the section where they were -defined. Doing this ensures that each symbol points to its containing -section. Each symbol also has a varying amount of hidden -private data for the BFD back end. Since the symbol points to the -original file, the private data format for that symbol is accessible. -@code{ld} can operate on a collection of symbols of wildly different -formats without problems. - -Normal global and simple local symbols are maintained on output, so an -output file (no matter its format) will retain symbols pointing to -functions and to global, static, and common variables. Some symbol -information is not worth retaining; in @code{a.out}, type information is -stored in the symbol table as long symbol names. This information would -be useless to most COFF debuggers and may be thrown away with -appropriate command line switches. (The GNU debugger @code{gdb} does -support @code{a.out} style debugging information in COFF). - -There is one word of type information within the symbol, so if the -format supports symbol type information within symbols (for example, COFF, -IEEE, Oasys) and the type is simple enough to fit within one word -(nearly everything but aggregates), the information will be preserved. - -@item relocation level -Each canonical BFD relocation record contains a pointer to the symbol to -relocate to, the offset of the data to relocate, the section the data -is in, and a pointer to a relocation type descriptor. Relocation is -performed by passing messages through the relocation type -descriptor and the symbol pointer. Therefore, relocations can be performed -on output data using a relocation method that is only available in one of the -input formats. For instance, Oasys provides a byte relocation format. -A relocation record requesting this relocation type would point -indirectly to a routine to perform this, so the relocation may be -performed on a byte being written to a COFF file, even though 68k COFF -has no such relocation type. -@c FIXME why specific reference to 68K above? - -@item line numbers -Object formats can contain, for debugging purposes, some form of mapping -between symbols, source line numbers, and addresses in the output file. -These addresses have to be relocated along with the symbol information. -Each symbol with an associated list of line number records points to the -first record of the list. The head of a line number list consists of a -pointer to the symbol, which allows finding out the address of the -function whose line number is being described. The rest of the list is -made up of pairs: offsets into the section and line numbers. Any format -which can simply derive this information can pass it successfully -between formats (COFF, IEEE and Oasys). -@end table +@include ../bfd/doc/bfdsumm.texi @end ifclear @node MRI |