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[ClangScanDeps] Avoid use-of-uninitialized-memory for end-of-directive edge case (#188590)

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https://github.com/llvm/llvm-project/pull/186966 was reverted because
the test case triggered a use-of-uninitialized-memory
(https://lab.llvm.org/buildbot/#/builders/94/builds/16379), due to the
include directive omitting a trailing newline. This patch adds a minor
fix to avoid the use-of-uninitialized-memory, and deliberately re-adds
the test case sans trailing newline for regression testing.

MSan report prior to this fix:
```
@@@BUILD_STEP sanitizer logs: stage2/msan_track_origins check@@@
==clang-scan-deps==616960==WARNING: MemorySanitizer: use-of-uninitialized-value
    #0 0x5555599c3300 in isAnnotation /home/b/sanitizer-x86_64-linux-bootstrap-msan/build/llvm-project/clang/include/clang/Lex/Token.h:131:38
    #1 0x5555599c3300 in setLength /home/b/sanitizer-x86_64-linux-bootstrap-msan/build/llvm-project/clang/include/clang/Lex/Token.h:152:13
    #2 0x5555599c3300 in clang::Lexer::FormTokenWithChars(clang::Token&, char const*, clang::tok::TokenKind) /home/b/sanitizer-x86_64-linux-bootstrap-msan/build/llvm-project/clang/include/clang/Lex/Lexer.h:644:12
    #3 0x5555599cf895 in clang::Lexer::LexEndOfFile(clang::Token&, char const*) /home/b/sanitizer-x86_64-linux-bootstrap-msan/build/llvm-project/clang/lib/Lex/Lexer.cpp:3166:5
    #4 0x555559bb229b in clang::Preprocessor::Lex(clang::Token&) /home/b/sanitizer-x86_64-linux-bootstrap-msan/build/llvm-project/clang/lib/Lex/Preprocessor.cpp:916:11
    #5 0x555559aa5365 in __invoke<void (clang::Preprocessor::*&)(clang::Token &), clang::Preprocessor *, clang::Token &> /home/b/sanitizer-x86_64-linux-bootstrap-msan/build/libcxx_install_msan_track_origins/include/c++/v1/__type_traits/invoke.h:90:27
    #6 0x555559aa5365 in invoke<void (clang::Preprocessor::*&)(clang::Token &), clang::Preprocessor *, clang::Token &> /home/b/sanitizer-x86_64-linux-bootstrap-msan/build/libcxx_install_msan_track_origins/include/c++/v1/__functional/invoke.h:29:10
    #7 0x555559aa5365 in operator()<void (clang::Preprocessor::*)(clang::Token &)> /home/b/sanitizer-x86_64-linux-bootstrap-msan/build/llvm-project/clang/lib/Lex/PPDirectives.cpp:470:5
    #8 0x555559aa5365 in clang::Preprocessor::CheckEndOfDirective(llvm::StringRef, bool, llvm::SmallVectorImpl<clang::Token>*) /home/b/sanitizer-x86_64-linux-bootstrap-msan/build/llvm-project/clang/lib/Lex/PPDirectives.cpp:478:5
    #9 0x555559ab96b5 in clang::Preprocessor::HandleIncludeDirective(clang::SourceLocation, clang::Token&, clang::detail::SearchDirIteratorImpl<true>, clang::FileEntry const*) /home/b/sanitizer-x86_64-linux-bootstrap-msan/build/llvm-project/clang/lib/Lex/PPDirectives.cpp:2205:7
    ...
```
This commit is contained in:
Thurston Dang 2026-03-26 22:27:45 -07:00 committed by GitHub
parent 9c98207e16
commit f1889a73e6
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2 changed files with 28 additions and 0 deletions
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3
clang/lib/Lex/PPDirectives.cpp
View File

@ -466,6 +466,9 @@ SourceLocation
Preprocessor::CheckEndOfDirective(StringRef DirType, bool EnableMacros,
SmallVectorImpl<Token> *ExtraToks) {
Token Tmp;
// Avoid use-of-uninitialized-memory for edge case(s) where there is no extra
// token to be parsed.
Tmp.startToken();
auto ReadNextTok = [this, ExtraToks, &Tmp](auto &&LexFn) {
std::invoke(LexFn, this, Tmp);
if (ExtraToks && Tmp.isNot(tok::eod))

25
clang/test/ClangScanDeps/p1689-suppress-warnings-no-eol.cppm Normal file
View File

@ -0,0 +1,25 @@
// Test that there is no use-of-uninitialized memory when parsing '#include' in
// the last line, without a newline.
//
// Forked from p1689-suppress-warnings.cppm.
// RUN: rm -rf %t
// RUN: mkdir -p %t
// RUN: split-file %s %t
// Test P1689 format - should NOT emit warnings
// RUN: clang-scan-deps -format=p1689 -- %clang++ -std=c++20 -I%t -c %t/mylib.cppm -o %t/mylib.o 2>&1 | FileCheck %s
// CHECK-NOT: warning:
// CHECK: {
// CHECK: "revision"
//--- header.h
// Empty header for testing
//--- mylib.cppm
module;
export module mylib;
#include <header.h>