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[LLD][COFF] Add /nodbgdirmerge to control debug directory section #159235

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Merged
mstorsjo merged 4 commits into from
Sep 19, 2025
Merged

[LLD][COFF] Add /nodbgdirmerge to control debug directory section #159235

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080d7fe
[LLD][COFF] Add /nodbgdirmerge to control debug directory section
kkent030315 Sep 17, 2025
6e50b67
fix typo
kkent030315 Sep 17, 2025
64442af
fix inverted eval
kkent030315 Sep 17, 2025
258eec2
fix tests
kkent030315 Sep 17, 2025
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1 change: 1 addition & 0 deletions lld/COFF/Config.h
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Original file line number Diff line number Diff line change
Expand Up @@ -322,6 +322,7 @@ struct Configuration {
bool largeAddressAware = false;
bool highEntropyVA = false;
bool appContainer = false;
bool mergeDebugDirectory = true;
bool mingw = false;
bool warnMissingOrderSymbol = true;
bool warnLocallyDefinedImported = true;
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3 changes: 3 additions & 0 deletions lld/COFF/Driver.cpp
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Expand Up @@ -2338,6 +2338,9 @@ void LinkerDriver::linkerMain(ArrayRef<const char *> argsArr) {
config->is64() &&
args.hasFlag(OPT_highentropyva, OPT_highentropyva_no, true);

// Handle /nodbgdirmerge
config->mergeDebugDirectory = !args.hasArg(OPT_nodbgdirmerge);

if (!config->dynamicBase &&
(config->machine == ARMNT || isAnyArm64(config->machine)))
Err(ctx) << "/dynamicbase:no is not compatible with "
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2 changes: 2 additions & 0 deletions lld/COFF/Options.td
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Expand Up @@ -90,6 +90,8 @@ def machine : P<"machine", "Specify target platform">;
def merge : P<"merge", "Combine sections">;
def mllvm : P<"mllvm", "Options to pass to LLVM">;
def nodefaultlib : P<"nodefaultlib", "Remove a default library">;
def nodbgdirmerge : F<"nodbgdirmerge">,
HelpText<"Emit the debug directory in a separate section">;
def opt : P<"opt", "Control optimizations">;
def order : P<"order", "Put functions in order">;
def out : P<"out", "Path to file to write output">;
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10 changes: 9 additions & 1 deletion lld/COFF/Writer.cpp
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Expand Up @@ -324,6 +324,7 @@ class Writer {
OutputSection *bssSec;
OutputSection *rdataSec;
OutputSection *buildidSec;
OutputSection *cvinfoSec;
OutputSection *dataSec;
OutputSection *pdataSec;
OutputSection *idataSec;
Expand Down Expand Up @@ -1092,6 +1093,7 @@ void Writer::createSections() {
bssSec = createSection(".bss", bss | r | w);
rdataSec = createSection(".rdata", data | r);
buildidSec = createSection(".buildid", data | r);
cvinfoSec = createSection(".cvinfo", data | r);
dataSec = createSection(".data", data | r | w);
pdataSec = createSection(".pdata", data | r);
idataSec = createSection(".idata", data | r);
Expand Down Expand Up @@ -1228,7 +1230,13 @@ void Writer::createMiscChunks() {
});

// Create Debug Information Chunks
debugInfoSec = config->mingw ? buildidSec : rdataSec;
if (config->mingw) {
debugInfoSec = buildidSec;
} else if (!config->mergeDebugDirectory) {
debugInfoSec = cvinfoSec;
} else {
debugInfoSec = rdataSec;
}
if (config->buildIDHash != BuildIDHash::None || config->debug ||
config->repro || config->cetCompat || config->cetCompatStrict ||
config->cetCompatIpValidationRelaxed ||
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33 changes: 33 additions & 0 deletions lld/test/COFF/nodbgdirmerge.test
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@@ -0,0 +1,33 @@
RUN: yaml2obj %p/Inputs/pdb1.yaml -o %t1.obj
RUN: yaml2obj %p/Inputs/pdb2.yaml -o %t2.obj
RUN: rm -f %t.dll %t.pdb

## Check that it emits the debug directory in .cvinfo section when
## /nodbgdirmerge is specified
RUN: lld-link /debug /pdb:%t.pdb /pdbaltpath:test.pdb /dll /out:%t.dll \
RUN: /entry:main /nodefaultlib /nodbgdirmerge %t1.obj %t2.obj
RUN: llvm-readobj --sections %t.dll | FileCheck -check-prefix=CHECKNOTMERGED %s

CHECKNOTMERGED: Section {
CHECKNOTMERGED: Number: 3
CHECKNOTMERGED-NEXT: Name: .cvinfo
CHECKNOTMERGED-NEXT: VirtualSize: 0x3D
CHECKNOTMERGED-NEXT: VirtualAddress: 0x3000
CHECKNOTMERGED-NEXT: RawDataSize: 512
CHECKNOTMERGED-NEXT: PointerToRawData: 0x800
CHECKNOTMERGED-NEXT: PointerToRelocations: 0
CHECKNOTMERGED-NEXT: PointerToLineNumbers: 0
CHECKNOTMERGED-NEXT: RelocationCount: 0
CHECKNOTMERGED-NEXT: LineNumberCount: 0
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@mstorsjo mstorsjo Sep 17, 2025

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This is fine as is - but as a general comment; it's also possible to make the test less prone to breaking on unrelated changes, by entirely omitting the values on the lines we're not interested in - it still matches the line so we can use -NEXT to keep things connected, but still matching those lines fuzzily.

Another potential approach is to skip -NEXT for the section we're not that interested in, then have e.g. CHECKNOTMERGED: LineNumberCount: CHECKNOTMERGED-NEXT: Characteristics [ (0x40000040), so the check for LineNumberCount: certainly will match the next such line, and force the full exact match on Characteristics to still be the next one (i.e. in the same section).

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@kkent030315 kkent030315 Sep 17, 2025

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We just need to check the presense of .cvinfo section and that's all, perhaps it should suffice we just have single line CHECKNOTMERGED: Name: .cvinfo as well as the negate test?

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@mstorsjo mstorsjo Sep 17, 2025

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Yes, that would probably also suffice. I guess technically we maybe also could want to check the contents of the section (not only that the section exists but also contains roughly the expected contents), but you're right that the rest of these checks here are kinda redundant.

CHECKNOTMERGED-NEXT: Characteristics [ (0x40000040)
CHECKNOTMERGED-NEXT: IMAGE_SCN_CNT_INITIALIZED_DATA (0x40)
CHECKNOTMERGED-NEXT: IMAGE_SCN_MEM_READ (0x40000000)
CHECKNOTMERGED-NEXT: ]
CHECKNOTMERGED-NEXT: }

## Check that it triggers merge on when /nodbgdirmerge is not specified
RUN: lld-link /debug /pdb:%t.pdb /pdbaltpath:test.pdb /dll /out:%t.dll \
RUN: /entry:main /nodefaultlib %t1.obj %t2.obj
RUN: llvm-readobj --sections %t.dll | FileCheck -check-prefix=CHECKMERGED %s

CHECKMERGED-NOT: Name: .cvinfo