================
@@ -6331,26 +6321,79 @@ static StringLiteralCheckType checkFormatStringExpr(
}
}
- return SLCT_NotALiteral;
+ // try to constant-evaluate the string
+ break;
}
default:
+ // try to constant-evaluate the string
+ break;
+ }
+
+ const StringLiteral *FakeLiteral = nullptr;
+ switch (constEvalStringAsLiteral(S, E, FakeLiteral)) {
+ case SLCER_NotEvaluated:
return SLCT_NotALiteral;
+
+ case SLCER_NotNullTerminated:
+ S.Diag(Args[format_idx]->getBeginLoc(),
+ diag::warn_printf_format_string_not_null_terminated)
+ << Args[format_idx]->getSourceRange();
+ if (!InFunctionCall)
+ S.Diag(E->getBeginLoc(), diag::note_format_string_defined);
+ // Stop checking, as this might just mean we're missing a chunk of the
+ // format string and there would be other spurious format issues.
+ return SLCT_UncheckedLiteral;
+
+ case SLCER_Evaluated:
+ InFunctionCall = false;
+ E = FakeLiteral;
+ goto tryAgain;
}
}
-// If this expression can be evaluated at compile-time,
-// check if the result is a StringLiteral and return it
-// otherwise return nullptr
-static const Expr *maybeConstEvalStringLiteral(ASTContext &Context,
- const Expr *E) {
+static StringLiteralConstEvalResult
+constEvalStringAsLiteral(Sema &S, const Expr *E, const StringLiteral *&SL) {
+ // As a last resort, try to constant-evaluate the format string. If it
+ // evaluates to a string literal in the first place, we can point to that
+ // string literal in source and use that.
Expr::EvalResult Result;
- if (E->EvaluateAsRValue(Result, Context) && Result.Val.isLValue()) {
+ if (E->EvaluateAsRValue(Result, S.Context) && Result.Val.isLValue()) {
const auto *LVE = Result.Val.getLValueBase().dyn_cast<const Expr *>();
- if (isa_and_nonnull<StringLiteral>(LVE))
- return LVE;
+ if (auto *BaseSL = dyn_cast_or_null<StringLiteral>(LVE)) {
+ SL = BaseSL;
+ return SLCER_Evaluated;
+ }
}
- return nullptr;
+
+ // Otherwise, try to evaluate the expression as a string constant.
+ std::string FormatString;
+ if (!E->tryEvaluateString(S.Context, FormatString)) {
+ return FormatString.empty() ? SLCER_NotEvaluated : SLCER_NotNullTerminated;
+ }
+
+ std::unique_ptr<llvm::MemoryBuffer> MemBuf;
+ {
+ llvm::SmallString<80> EscapedString;
+ {
+ llvm::raw_svector_ostream OS(EscapedString);
+ OS << '"';
+ OS.write_escaped(FormatString);
----------------
apple-fcloutier wrote:
I tried with `-fixit` and had the same result. For clang-tidy, I tried this:
```
% cat /tmp/test.c
__attribute__((format(printf, 1, 2)))
int printf(const char *, ...);
int main() {
const char buf[] = {'"', '%', 's', '"', 0};
printf(buf, 123);
printf("%s", 123);
}
% bin/clang-tidy --fix /tmp/test.c
....
2 warnings generated.
/tmp/test.c:6:17: warning: format specifies type 'char *' but the argument has
type 'int' [clang-diagnostic-format]
6 | printf(buf, 123);
| ~~~ ^~~
note: format string resolved to a constant string
/tmp/test.c:7:18: warning: format specifies type 'char *' but the argument has
type 'int' [clang-diagnostic-format]
7 | printf("%s", 123);
| ~~ ^~~
| %d
/tmp/test.c:7:13: note: FIX-IT applied suggested code changes
7 | printf("%s", 123);
| ^
clang-tidy applied 1 of 1 suggested fixes.
```
In words: it fixes the `printf("%s", 123)` line to use `%d` and leaves alone
the other printf alone without throwing a fuss (claiming "clang-tidy applied 1
of 1 suggested fixes"). Clang-tidy shows the "format string resolved to a
constant string" note but not the scratch space contents. It's not ideal, but
it's quite reasonable IMO.
https://github.com/llvm/llvm-project/pull/135864
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