xbolva00 created this revision.
xbolva00 added a reviewer: aaron.ballman.
Herald added a project: clang.
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xbolva00 marked an inline comment as done.
xbolva00 added inline comments.
================
Comment at: clang/test/Sema/warn-stringcompare.c:4-6
+#define DELIM "/"
+#define NULL (void *)0
+
----------------
Current behaviour: https://godbolt.org/z/7nYH6N
As noted in PR, we have a poor test coverage for this warning. I think macro
support was just overlooked. GCC warns in these cases.
Clang missed a real bug in the code I am working with, GCC caught it.
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D70624
Files:
clang/include/clang/Basic/DiagnosticSemaKinds.td
clang/lib/Sema/SemaExpr.cpp
clang/test/Sema/exprs.c
clang/test/Sema/warn-stringcompare.c
Index: clang/test/Sema/warn-stringcompare.c
===================================================================
--- /dev/null
+++ clang/test/Sema/warn-stringcompare.c
@@ -0,0 +1,20 @@
+// RUN: %clang_cc1 -x c -fsyntax-only -verify %s
+// RUN: %clang_cc1 -x c++ -fsyntax-only -verify %s
+
+#define DELIM "/"
+#define NULL (void *)0
+
+void test(const char *d) {
+ if ("/" != d) // expected-warning {{result of comparison against a string literal is unspecified}}
+ return;
+ if (d == "/") // expected-warning {{result of comparison against a string literal is unspecified}}
+ return;
+ if ("/" != NULL)
+ return;
+ if (NULL == "/")
+ return;
+ if ("/" != DELIM) // expected-warning {{result of comparison against a string literal is unspecified}}
+ return;
+ if (DELIM == "/") // expected-warning {{result of comparison against a string literal is unspecified}}
+ return;
+}
Index: clang/test/Sema/exprs.c
===================================================================
--- clang/test/Sema/exprs.c
+++ clang/test/Sema/exprs.c
@@ -119,7 +119,7 @@
// PR3753
int test12(const char *X) {
- return X == "foo"; // expected-warning {{comparison against a string literal is unspecified (use strncmp instead)}}
+ return X == "foo"; // expected-warning {{comparison against a string literal is unspecified}}
}
int test12b(const char *X) {
Index: clang/lib/Sema/SemaExpr.cpp
===================================================================
--- clang/lib/Sema/SemaExpr.cpp
+++ clang/lib/Sema/SemaExpr.cpp
@@ -10338,7 +10338,6 @@
QualType RHSType = RHS->getType();
if (LHSType->hasFloatingRepresentation() ||
(LHSType->isBlockPointerType() && !BinaryOperator::isEqualityOp(Opc)) ||
- LHS->getBeginLoc().isMacroID() || RHS->getBeginLoc().isMacroID() ||
S.inTemplateInstantiation())
return;
@@ -10366,45 +10365,51 @@
AlwaysEqual, // std::strong_ordering::equal from operator<=>
};
- 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)) {
+ 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;
+ }
+ S.DiagRuntimeBehavior(Loc, nullptr,
+ S.PDiag(diag::warn_comparison_always)
+ << 1 /*array comparison*/
+ << Result);
}
- S.DiagRuntimeBehavior(Loc, nullptr,
- S.PDiag(diag::warn_comparison_always)
- << 1 /*array comparison*/
- << Result);
}
if (isa<CastExpr>(LHSStripped))
Index: clang/include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -8428,8 +8428,7 @@
def warn_stringcompare : Warning<
"result of comparison against %select{a string literal|@encode}0 is "
- "unspecified (use strncmp instead)">,
- InGroup<StringCompare>;
+ "unspecified">, InGroup<StringCompare>;
def warn_identity_field_assign : Warning<
"assigning %select{field|instance variable}0 to itself">,
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