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Don't Mutate ModuleDecl's File List When Creating Synthesized Files

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See #59144 for more on why this is a bad idea.

Patch out the synthesized file unit accessor to only clear the source cache, then patch up all the places that were assuming they could iterate over the module's file list and see synthesized files.

rdar://94164512
This commit is contained in:
Robert Widmann
2022-06-11 11:07:05 -06:00
parent 1c76e22c84
commit 0d117c1345
6 changed files with 34 additions and 29 deletions
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31
lib/AST/Module.cpp
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@@ -320,13 +320,13 @@ SourceLookupCache::SourceLookupCache(const ModuleDecl &M) {
FrontendStatsTracer tracer(M.getASTContext().Stats,
"module-populate-cache");
for (const FileUnit *file : M.getFiles()) {
if (auto *SFU = dyn_cast<SynthesizedFileUnit>(file)) {
addToUnqualifiedLookupCache(SFU->getTopLevelDecls(), false);
continue;
}
auto *SF = cast<SourceFile>(file);
addToUnqualifiedLookupCache(SF->getTopLevelDecls(), false);
addToUnqualifiedLookupCache(SF->getHoistedDecls(), false);
if (auto *SFU = file->getSynthesizedFile()) {
addToUnqualifiedLookupCache(SFU->getTopLevelDecls(), false);
}
}
}
@@ -548,9 +548,13 @@ SourceFile *CodeCompletionFileRequest::evaluate(Evaluator &evaluator,
llvm_unreachable("Couldn't find the completion file?");
}
#define FORWARD(name, args) \
for (const FileUnit *file : getFiles()) \
file->name args;
#define FORWARD(name, args) \
for (const FileUnit *file : getFiles()) { \
file->name args; \
if (auto *synth = file->getSynthesizedFile()) { \
synth->name args; \
} \
}
SourceLookupCache &ModuleDecl::getSourceLookupCache() const {
if (!Cache) {
@@ -3064,16 +3068,9 @@ SynthesizedFileUnit &FileUnit::getOrCreateSynthesizedFile() {
return *thisSynth;
SynthesizedFile = new (getASTContext()) SynthesizedFileUnit(*this);
SynthesizedFileAndKind.setPointer(SynthesizedFile);
// FIXME: Mutating the module in-flight is not a good idea. Any
// callers above us in the stack that are iterating over
// the module's files will have their iterators invalidated. There's
// a strong chance that whatever analysis led to this function being
// called is doing just that!
//
// Instead we ought to just call ModuleDecl::clearLookupCache() here
// and patch out the places looking for synthesized files hanging off of
// source files.
getParentModule()->addFile(*SynthesizedFile);
// Rebuild the source lookup caches now that we have a synthesized file
// full of declarations to look into.
getParentModule()->clearLookupCache();
}
return *SynthesizedFile;
}