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Reland "[mac/lld] Implement -why_load".

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The problem was that `sym` became replaced in the call
to make<ObjFile> and referring to it afer that read memory that now
stored a different kind of symbol (a Defined instead of a LazySymbol).
Since this happens only once per archive, just copy the symbol to the
stack before make<ObjFile> and read the copy instead.

Originally reviewed at https://reviews.llvm.org/D92496
This commit is contained in:
Nico Weber 2020-12-02 18:59:00 -05:00
parent d3fef7a7c2
commit 3422f3cc6e
7 changed files with 109 additions and 2 deletions
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1
lld/MachO/Config.h
View File

@ -38,6 +38,7 @@ struct Configuration {
bool staticLink = false;
bool isPic = false;
bool headerPadMaxInstallNames = false;
bool printWhyLoad = false;
bool searchDylibsFirst = false;
bool saveTemps = false;
uint32_t headerPad;

4
lld/MachO/Driver.cpp
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@ -275,6 +275,8 @@ static InputFile *addFile(StringRef path, bool forceLoadArchive) {
for (const ArchiveMember &member : getArchiveMembers(*buffer)) {
inputFiles.push_back(
make<ObjFile>(member.mbref, member.modTime, path));
printWhyLoad((forceLoadArchive ? "-force_load" : "-all_load"),
inputFiles.back());
}
}
} else if (config->forceLoadObjC) {
@ -291,6 +293,7 @@ static InputFile *addFile(StringRef path, bool forceLoadArchive) {
if (hasObjCSection(member.mbref)) {
inputFiles.push_back(
make<ObjFile>(member.mbref, member.modTime, path));
printWhyLoad("-ObjC", inputFiles.back());
}
}
}
@ -637,6 +640,7 @@ bool macho::link(llvm::ArrayRef<const char *> argsArr, bool canExitEarly,
config->headerPad = args::getHex(args, OPT_headerpad, /*Default=*/32);
config->headerPadMaxInstallNames =
args.hasArg(OPT_headerpad_max_install_names);
config->printWhyLoad = args.hasArg(OPT_why_load);
config->outputType = getOutputType(args);
config->runtimePaths = args::getStrings(args, OPT_rpath);
config->allLoad = args.hasArg(OPT_all_load);

3
lld/MachO/Driver.h
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@ -19,6 +19,7 @@ namespace lld {
namespace macho {
class DylibFile;
class InputFile;
class MachOOptTable : public llvm::opt::OptTable {
public:
@ -45,6 +46,8 @@ llvm::Optional<DylibFile *> makeDylibFromTAPI(llvm::MemoryBufferRef mbref,
uint32_t getModTime(llvm::StringRef path);
void printWhyLoad(StringRef reason, const InputFile *);
} // namespace macho
} // namespace lld

8
lld/MachO/DriverUtils.cpp
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@ -7,6 +7,7 @@
//===----------------------------------------------------------------------===//
#include "Driver.h"
#include "Config.h"
#include "InputFiles.h"
#include "lld/Common/Args.h"
@ -185,3 +186,10 @@ uint32_t macho::getModTime(StringRef path) {
warn("failed to get modification time of " + path);
return 0;
}
void macho::printWhyLoad(StringRef reason, const InputFile *f) {
if (!config->printWhyLoad)
return;
lld::outs() << reason << " forced load of " << toString(f)
<< '\n';
}

9
lld/MachO/InputFiles.cpp
View File

@ -619,8 +619,17 @@ void ArchiveFile::fetch(const object::Archive::Symbol &sym) {
"for the member defining symbol " +
toMachOString(sym)));
// `sym` is owned by a LazySym, which will be replace<>() by make<ObjFile>
// and become invalid after that call. Copy it to the stack so we can refer
// to it later.
const object::Archive::Symbol sym_copy = sym;
auto file = make<ObjFile>(mb, modTime, getName());
// ld64 doesn't demangle sym here even with -demangle. Match that, so
// intentionally no call to toMachOString() here.
printWhyLoad(sym_copy.getName(), file);
symbols.insert(symbols.end(), file->symbols.begin(), file->symbols.end());
subsections.insert(subsections.end(), file->subsections.begin(),
file->subsections.end());

3
lld/MachO/Options.td
View File

@ -426,8 +426,7 @@ def commons : Separate<["-"], "commons">,
def grp_introspect : OptionGroup<"introspect">, HelpText<"INTROSPECTING THE LINKER">;
def why_load : Flag<["-"], "why_load">,
HelpText<"Log the symbol that compels loading of each object file from a static library">,
Flags<[HelpHidden]>,
HelpText<"Log why each object file is loaded from a static library">,
Group<grp_introspect>;
def whyload : Flag<["-"], "whyload">,
Alias<why_load>,

83
lld/test/MachO/why-load.s Normal file
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@ -0,0 +1,83 @@
# REQUIRES: x86
# RUN: rm -rf %t
# RUN: split-file %s %t
# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-macos -o %t/objc.o %t/objc.s
# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-macos -o %t/foo.o %t/foo.s
# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-macos -o %t/bar.o %t/bar.s
# RUN: llvm-ar csr %t/lib.a %t/objc.o %t/foo.o %t/bar.o
# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-macos -o %t/main.o %t/main.s
# The first line checks that we never demangle symbols in -why_load output.
# RUN: %lld %t/main.o %t/lib.a -o /dev/null -why_load -demangle | \
# RUN: FileCheck %s --check-prefix=WHY
# RUN: %lld %t/main.o -force_load %t/lib.a -o /dev/null -why_load | \
# RUN: FileCheck %s --check-prefix=WHYFORCE
# RUN: %lld %t/main.o %t/lib.a -o /dev/null -all_load -why_load | \
# RUN: FileCheck %s --check-prefix=WHYALL
# RUN: %lld %t/main.o -force_load %t/lib.a -o /dev/null -all_load -why_load | \
# RUN: FileCheck %s --check-prefix=WHYALLFORCE
# RUN: %lld %t/main.o %t/lib.a -o /dev/null -ObjC -why_load | \
# RUN: FileCheck %s --check-prefix=WHYOBJC
# RUN: %lld %t/main.o -force_load %t/lib.a -o /dev/null -ObjC -why_load | \
# RUN: FileCheck %s --check-prefix=WHYOBJCFORCE
# RUN: %lld %t/main.o %t/lib.a -o /dev/null -ObjC -all_load -why_load | \
# RUN: FileCheck %s --check-prefix=WHYOBJCALL
# RUN: %lld %t/main.o -force_load %t/lib.a -o /dev/null -ObjC -all_load -why_load | \
# RUN: FileCheck %s --check-prefix=WHYOBJCALLFORCE
# WHY-DAG: _bar forced load of lib.a(bar.o)
# WHY-DAG: __Z3foo forced load of lib.a(foo.o)
# WHY-NOT: {{.*}} forced load of lib.a(objc.o)
# WHYFORCE-DAG: -force_load forced load of lib.a(bar.o)
# WHYFORCE-DAG: -force_load forced load of lib.a(foo.o)
# WHYFORCE-DAG: -force_load forced load of lib.a(objc.o)
# WHYALL-DAG: -all_load forced load of lib.a(bar.o)
# WHYALL-DAG: -all_load forced load of lib.a(foo.o)
# WHYALL-DAG: -all_load forced load of lib.a(objc.o)
# WHYALLFORCE-DAG: -force_load forced load of lib.a(bar.o)
# WHYALLFORCE-DAG: -force_load forced load of lib.a(foo.o)
# WHYALLFORCE-DAG: -force_load forced load of lib.a(objc.o)
# WHYOBJC-DAG: _bar forced load of lib.a(bar.o)
# WHYOBJC-DAG: __Z3foo forced load of lib.a(foo.o)
# WHYOBJC-DAG: -ObjC forced load of lib.a(objc.o)
# WHYOBJCFORCE-DAG: -force_load forced load of lib.a(bar.o)
# WHYOBJCFORCE-DAG: -force_load forced load of lib.a(foo.o)
# WHYOBJCFORCE-DAG: -force_load forced load of lib.a(objc.o)
# WHYOBJCALL-DAG: -all_load forced load of lib.a(bar.o)
# WHYOBJCALL-DAG: -all_load forced load of lib.a(foo.o)
# WHYOBJCALL-DAG: -all_load forced load of lib.a(objc.o)
# WHYOBJCALLFORCE-DAG: -force_load forced load of lib.a(bar.o)
# WHYOBJCALLFORCE-DAG: -force_load forced load of lib.a(foo.o)
# WHYOBJCALLFORCE-DAG: -force_load forced load of lib.a(objc.o)
#--- objc.s
.section __DATA,__objc_catlist
.quad 0x1234
#--- foo.s
.globl __Z3foo
__Z3foo:
ret
#--- bar.s
.globl _bar
_bar:
callq __Z3foo
ret
#--- main.s
.globl _main
_main:
callq _bar
callq __Z3foo
ret