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[LLD] [COFF] Add a separate option for allowing duplicate weak symbols (#68077)

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The MinGW mode (enabled with the flag -lldmingw) does allow duplicate
weak symbols. A test in
compiler-rt/test/profile/Windows/coverage-weak-lld.cpp does currently
enable the -lldmingw flag in an MSVC context, in order to deal with
duplicate weak symbols.

Add a new, separate, lld specific flag for enabling this. In MinGW mode,
this is enabled by default, otherwise it is disabled.

This allows making the MinGW mode more restrictive in adding libpaths
from the surrounding environment; in MinGW mode, all libpaths are passed
explicitly by the compiler driver to the linker, which is attempted in
https://reviews.llvm.org/D144084.
This commit is contained in:
Martin Storsjö 2023-10-20 23:44:44 +03:00 committed by GitHub
parent c5dacb6d7a
commit a67ae8c0fd
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5 changed files with 11 additions and 1 deletions
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1
lld/COFF/Config.h
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@ -316,6 +316,7 @@ struct Configuration {
bool stdcallFixup = false;
bool writeCheckSum = false;
EmitKind emit = EmitKind::Obj;
bool allowDuplicateWeak = false;
};
} // namespace lld::coff

3
lld/COFF/Driver.cpp
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@ -2028,6 +2028,9 @@ void LinkerDriver::linkerMain(ArrayRef<const char *> argsArr) {
config->stdcallFixup =
args.hasFlag(OPT_stdcall_fixup, OPT_stdcall_fixup_no, config->mingw);
config->warnStdcallFixup = !args.hasArg(OPT_stdcall_fixup);
config->allowDuplicateWeak =
args.hasFlag(OPT_lld_allow_duplicate_weak,
OPT_lld_allow_duplicate_weak_no, config->mingw);
if (args.hasFlag(OPT_inferasanlibs, OPT_inferasanlibs_no, false))
warn("ignoring '/inferasanlibs', this flag is not supported");

2
lld/COFF/InputFiles.cpp
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@ -81,7 +81,7 @@ static void checkAndSetWeakAlias(COFFLinkerContext &ctx, InputFile *f,
// of another symbol emitted near the weak symbol.
// Just use the definition from the first object file that defined
// this weak symbol.
if (ctx.config.mingw)
if (ctx.config.allowDuplicateWeak)
return;
ctx.symtab.reportDuplicate(source, f);
}

1
lld/COFF/Options.td
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@ -232,6 +232,7 @@ defm demangle : B<"demangle",
def include_optional : Joined<["/", "-", "/?", "-?"], "includeoptional:">,
HelpText<"Add symbol as undefined, but allow it to remain undefined">;
def kill_at : F<"kill-at">;
defm lld_allow_duplicate_weak : B_priv<"lld-allow-duplicate-weak">;
def lldemit : P<"lldemit", "Specify output type">;
def lldmingw : F<"lldmingw">;
def noseh : F<"noseh">;

5
lld/test/COFF/gnu-weak.test
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@ -1,4 +1,9 @@
RUN: lld-link -lldmingw %S/Inputs/gnu-weak.o %S/Inputs/gnu-weak2.o -out:%t.exe
RUN: lld-link -lld-allow-duplicate-weak %S/Inputs/gnu-weak.o %S/Inputs/gnu-weak2.o -out:%t.exe
RUN: not lld-link %S/Inputs/gnu-weak.o %S/Inputs/gnu-weak2.o -out:%t.exe 2>&1 | FileCheck %s --check-prefix=DEFAULT-ERROR
DEFAULT-ERROR: error: duplicate symbol: weakfunc
GNU ld can handle several definitions of the same weak symbol, and
unless there is a strong definition of it, it just picks the first