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[llvm-mt] Add support /notify_update 

`/notify_update` is an undocumented feature used by CMake. From their usage, it looks like this feature just changes `mt`'s exit code if the output file was changed. See https://gitlab.kitware.com/cmake/cmake/-/blob/master/Source/cmcmd.cxx#L2300 this is also consistent with some testing I have done of the mt.exeshipped with Visual Studio. See also the comment at https://gitlab.kitware.com/cmake/cmake/-/blob/master/Source/cmcmd.cxx#L2440.

There might be a more performant way to implement this by first checking calling `llvm::sys::fs::file_size()` and if it is the same as the new output's size use `llvm::WritableMemoryBuffer` and fallback to `llvm::FileOutputBuffer` otherwise,  but these don't inherit from a common ancestor so any implementation doing this would be really ugly.

Fixes https://github.com/llvm/llvm-project/issues/54329

Reviewed By: phosek

Differential Revision: https://reviews.llvm.org/D121438
This commit is contained in:
Alex Brachet 2022-03-11 03:46:46 +00:00
parent a11d1cc41c
commit e970d2823c
3 changed files with 41 additions and 2 deletions
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16
llvm/test/tools/llvm-mt/notify_update.test Normal file
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@ -0,0 +1,16 @@
REQUIRES: libxml2
UNSUPPORTED: system-windows
Exits normally without /notify_update
RUN: llvm-mt /manifest %p/Inputs/test_manifest.manifest /out:%t.manifest
RUN: rm -f %t.manifest
We can't check exit code so all we can do is see if not considered it as a failure
File didn't exist previously so it's an update
RUN: not llvm-mt /manifest %p/Inputs/test_manifest.manifest /out:%t.manifest /notify_update
RUN: llvm-mt /manifest %p/Inputs/test_manifest.manifest /out:%t.manifest /notify_update
New manifest, so it's an update
RUN: not llvm-mt /manifest %p/Inputs/additional.manifest /out:%t.manifest /notify_update
RUN: llvm-mt /manifest %p/Inputs/additional.manifest /out:%t.manifest /notify_update

2
llvm/tools/llvm-mt/Opts.td
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@ -23,7 +23,7 @@ def validate_file_hashes : Joined<["/", "-"], "validate_file_hashes:">, HelpText
def canonicalize : Flag<["/", "-"], "canonicalize:">, HelpText<"Not supported">, Group<unsupported>;
def check_for_duplicates : Flag<["/", "-"], "check_for_duplicates:">, HelpText<"Not supported">, Group<unsupported>;
def make_cdfs : Flag<["/", "-"], "makecdfs:">, HelpText<"Not supported">, Group<unsupported>;
def notify_update : Flag<["/", "-"], "notify_update">, HelpText<"Not supported">, Group<unsupported>;
def notify_update : Flag<["/", "-"], "notify_update">, HelpText<"Exit with a special exit code if the output file has changed">;
def verbose : Flag<["/", "-"], "verbose">, HelpText<"Not supported">, Group<unsupported>;
def help : Flag<["/", "-"], "?">;
def help_long : Flag<["/", "-"], "help">, Alias<help>;

25
llvm/tools/llvm-mt/llvm-mt.cpp
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@ -141,6 +141,29 @@ int main(int Argc, const char **Argv) {
std::unique_ptr<MemoryBuffer> OutputBuffer = Merger.getMergedManifest();
if (!OutputBuffer)
reportError("empty manifest not written");
int ExitCode = 0;
if (InputArgs.hasArg(OPT_notify_update)) {
ErrorOr<std::unique_ptr<MemoryBuffer>> OutBuffOrErr =
MemoryBuffer::getFile(OutputFile);
// Assume if we couldn't open the output file then it doesn't exist meaning
// there was a change.
bool Same = false;
if (OutBuffOrErr) {
const std::unique_ptr<MemoryBuffer> &FileBuffer = *OutBuffOrErr;
Same = std::equal(OutputBuffer->getBufferStart(),
OutputBuffer->getBufferEnd(),
FileBuffer->getBufferStart());
}
if (!Same) {
#if LLVM_ON_UNIX
ExitCode = 0xbb;
#elif defined(_WIN32)
ExitCode = 0x41020001;
#endif
}
}
Expected<std::unique_ptr<FileOutputBuffer>> FileOrErr =
FileOutputBuffer::create(OutputFile, OutputBuffer->getBufferSize());
if (!FileOrErr)
@ -149,5 +172,5 @@ int main(int Argc, const char **Argv) {
std::copy(OutputBuffer->getBufferStart(), OutputBuffer->getBufferEnd(),
FileBuffer->getBufferStart());
error(FileBuffer->commit());
return 0;
return ExitCode;
}