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doc: Add a description for a useful case of mangling symbols

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Signed-off-by: Chang S. Bae <changseok.bae@gmail.com>
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Chang S. Bae 2018-10-29 16:16:16 -07:00 committed by Cyrill Gorcunov
parent 4b5b737d49
commit 4310eb9d42
1 changed files with 15 additions and 3 deletions
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18
doc/nasmdoc.src
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@ -4707,6 +4707,18 @@ This is a macro implemented as a \c{%pragma}:
Commandline option is also possible. See also \k{opt-pfix}.
Some tool chain is aware of a particular prefix for its own optimization
options, such as code elimination. For instance, Mach-O backend has a
linker that uses a simplistic naming scheme to chunk up sections into a
meta section. When the \c{subsections_via_symbols} directive
(\k{macho-ssvs}) is declared, each symbol is the start of a
separate block. The meta section is, then, defined to include sections
before the one that starts with a 'L'. \c{LPREFIX} is useful here to mark
all local symbols with the 'L' prefix to be excluded to the meta section.
It converts local symbols compatible with the particular tool chain.
Note that local symbols declared with \c{STATIC} (\k{static})
are excluded from the symbol mangling and also not marked as global.
\H{gen-namespace} \i\c{OUTPUT}, \i\c{DEBUG}: Generic Namespaces
@ -5823,9 +5835,9 @@ right-hand side of the \c{WRT} operator:
\S{macho-ssvs} \c{macho} specfic directive \i\c{subsections_via_symbols}
The directive \c{subsections_via_symbols} sets the
\c{MH_SUBSECTIONS_VIA_SYMBOLS} flag in the Mach-O header, which tells
the linker that the symbols in the file matches the conventions
required to allow for link-time dead code elimination.
\c{MH_SUBSECTIONS_VIA_SYMBOLS} flag in the Mach-O header, that effectively
separates a block (or a subsection) based on a symbol. It is often used
for eliminating dead codes by a linker.
This directive takes no arguments.