aaron.ballman added inline comments.
================
Comment at: clang/include/clang/Basic/DiagnosticSemaKinds.td:8431
"result of comparison against %select{a string literal|@encode}0 is "
- "unspecified (use strncmp instead)">,
- InGroup<StringCompare>;
+ "unspecified">, InGroup<StringCompare>;
----------------
I think this is a regression in the diagnostic because we dropped the
recommendation for how to fix the issue. Why do we need to drop that? I'd be
fine if it was made less specific, like: `(use an explicit string comparison
function instead)` if the concern is over `strncmp` specifically.
================
Comment at: clang/lib/Sema/SemaExpr.cpp:10368
- if (Expr::isSameComparisonOperand(LHS, RHS)) {
- unsigned Result;
- switch (Opc) {
- case BO_EQ: case BO_LE: case BO_GE:
- Result = AlwaysTrue;
- break;
- case BO_NE: case BO_LT: case BO_GT:
- Result = AlwaysFalse;
- break;
- case BO_Cmp:
- Result = AlwaysEqual;
- break;
- default:
- Result = AlwaysConstant;
- break;
- }
- S.DiagRuntimeBehavior(Loc, nullptr,
- S.PDiag(diag::warn_comparison_always)
- << 0 /*self-comparison*/
- << Result);
- } else if (checkForArray(LHSStripped) && checkForArray(RHSStripped)) {
- // What is it always going to evaluate to?
- unsigned Result;
- switch(Opc) {
- case BO_EQ: // e.g. array1 == array2
- Result = AlwaysFalse;
- break;
- case BO_NE: // e.g. array1 != array2
- Result = AlwaysTrue;
- break;
- default: // e.g. array1 <= array2
- // The best we can say is 'a constant'
- Result = AlwaysConstant;
- break;
+ if (!LHS->getBeginLoc().isMacroID() && !RHS->getBeginLoc().isMacroID()) {
+ if (Expr::isSameComparisonOperand(LHS, RHS)) {
----------------
Why do we care about the macros here? It seems just as reasonable to warn on:
```
#define MACRO1 "one"
#define MACRO2 "one
if (MACRO1 == MACRO2) // Why not warn here too?
```
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D70624/new/
https://reviews.llvm.org/D70624
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