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fix stack traces on macos when passing absolute path to root source file 

The comment added by this commit is copied here:

For macOS stack traces, we want to avoid having to parse the compilation unit debug
info. As long as each debug info file has a path independent of the compilation unit
directory (DW_AT_comp_dir), then we never have to look at the compilation unit debug
info. If we provide an absolute path to LLVM here for the compilation unit debug info,
LLVM will emit DWARF info that depends on DW_AT_comp_dir. To avoid this, we pass "."
for the compilation unit directory. This forces each debug file to have a directory
rather than be relative to DW_AT_comp_dir. According to DWARF 5, debug files will
no longer reference DW_AT_comp_dir, for the purpose of being able to support the
common practice of stripping all but the line number sections from an executable.

closes #2700
master
Andrew Kelley 2019-09-03 13:02:46 -04:00
parent e9530ce97b
commit e673d865fb
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2 changed files with 15 additions and 1 deletions
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15
src/codegen.cpp
View File

@ -8457,8 +8457,21 @@ static void init(CodeGen *g) {
Buf *producer = buf_sprintf("zig %d.%d.%d", ZIG_VERSION_MAJOR, ZIG_VERSION_MINOR, ZIG_VERSION_PATCH);
const char *flags = "";
unsigned runtime_version = 0;
// For macOS stack traces, we want to avoid having to parse the compilation unit debug
// info. As long as each debug info file has a path independent of the compilation unit
// directory (DW_AT_comp_dir), then we never have to look at the compilation unit debug
// info. If we provide an absolute path to LLVM here for the compilation unit debug info,
// LLVM will emit DWARF info that depends on DW_AT_comp_dir. To avoid this, we pass "."
// for the compilation unit directory. This forces each debug file to have a directory
// rather than be relative to DW_AT_comp_dir. According to DWARF 5, debug files will
// no longer reference DW_AT_comp_dir, for the purpose of being able to support the
// common practice of stripping all but the line number sections from an executable.
const char *compile_unit_dir = target_os_is_darwin(g->zig_target->os) ? "." :
buf_ptr(&g->root_package->root_src_dir);
ZigLLVMDIFile *compile_unit_file = ZigLLVMCreateFile(g->dbuilder, buf_ptr(g->root_out_name),
buf_ptr(&g->root_package->root_src_dir));
compile_unit_dir);
g->compile_unit = ZigLLVMCreateCompileUnit(g->dbuilder, ZigLLVMLang_DW_LANG_C99(),
compile_unit_file, buf_ptr(producer), is_optimized, flags, runtime_version,
"", 0, !g->strip_debug_symbols);

1
src/zig_llvm.cpp
View File

@ -842,6 +842,7 @@ const char *ZigLLVMGetSubArchTypeName(ZigLLVM_SubArchType sub_arch) {
void ZigLLVMAddModuleDebugInfoFlag(LLVMModuleRef module) {
unwrap(module)->addModuleFlag(Module::Warning, "Debug Info Version", DEBUG_METADATA_VERSION);
unwrap(module)->addModuleFlag(Module::Warning, "Dwarf Version", 4);
}
void ZigLLVMAddModuleCodeViewFlag(LLVMModuleRef module) {