njames93 added inline comments.
================
Comment at: clang/include/clang/ASTMatchers/ASTMatchers.h:313
+ AST_POLYMORPHIC_SUPPORTED_TYPES(Decl, Stmt, TypeLoc),
+ std::string, MacroName) {
// Verifies that the statement' beginning and ending are both expanded from
----------------
aaron.ballman wrote:
> You mentioned that the change from `StringRef` to `std::string` was to avoid
> lifetime issues while matching, but I'm wondering if you can expound on that
> situation a bit more. I would have assumed that any memoization that involves
> `StringRef` would be responsible for the lifetime issues rather than the
> matchers themselves, but maybe I'm thinking about a different way you can hit
> lifetime issues than you are.
Take this as contrived, however using ASAN reports a heap-use-after-free for
this code when isExpandedFromMacro takes a `StringRef` but works fine when
using `std::string`.
```lang=c++
TEST(IsExpandedFromMacro, IsExpandedFromMacro_MatchesDecls) {
auto Matcher =
isExpandedFromMacro(std::string("MY_MACRO_OVERFLOW_SMALL_STRING_SIZE"));//
<-Temporary string created and destroyed here.
StringRef input = R"cc(
#define MY_MACRO_OVERFLOW_SMALL_STRING_SIZE(a) int i = a;
void Test() { MY_MACRO_OVERFLOW_SMALL_STRING_SIZE(4); }
)cc";
EXPECT_TRUE(matches(input, varDecl(Matcher))); // <- heap-use-after-free
detected down the callstack from here.
}
```
Obviously this is very contrived to ensure asan detects the use-after-free and
to ensure the temporary string is destroyed before the matcher. For these tests
it doesn't look like a problem, but in other instances these matchers will
outlive a string being passed to them
```lang=c++
void addVarFromMacro(ASTMatchFinder* Finder, std::string MacroName) {
Finder->addMatcher(varDecl(isExpandedFromMacro(MacroName)), this);
}
```
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D90303/new/
https://reviews.llvm.org/D90303
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