Kevin Enderby 1a26f183b2 Change llvm-nm for Mach-O files to use dyld info in some cases when printing symbols. ...

In order to reduce swift binary sizes, Apple is now stripping swift symbols
from the nlist symbol table.  llvm-nm currently only looks at the nlist symbol
table and misses symbols that are present in dyld info.   This makes it hard to
know the set of symbols for a binary using just llvm-nm.  Unless you know to
run llvm-objdump -exports-trie that can output the exported symbols in the dyld
info from the export trie, which does so but in a different format.

Also moving forward the time may come a when a fully linked Mach-O file that
uses dyld will no longer have an nlist symbol table to avoid duplicating the
symbol information.

This change adds three flags to llvm-nm, -add-dyldinfo, -no-dyldinfo, and
-dyldinfo-only.

The first, -add-dyldinfo, has the same effect as when the new bit in the Mach-O
header, MH_NLIST_OUTOFSYNC_WITH_DYLDINFO, appears in a binary.  In that it
looks through the dyld info from the export trie and adds symbols to be printed
that are not already in its internal SymbolList variable.  The -no-dyldinfo
option turns this behavior off.

The -dyldinfo-only option only looks at the dyld information and recreates the
symbol table from the dyld info from the export trie and binding information.
As if it the Mach-O file had no nlist symbol table.

Also fixed a few bugs with Mach-O N_INDR symbols not correctly printing the
indirect name, or in the same format as the old nm-classic program.

rdar://32021551

llvm-svn: 305733

2017-06-19 19:38:22 +00:00

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