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Improve the diagnostic emitted when an unused ObjC property getter 

is found.  Instead of complaining about a generic "unused expr",
emit:
t.m:7:3: warning: property access result unused - getters should not have side effects

While objc property getters *could* have side effects, according to
the language best practices, they *shouldn't*.  Hopefully the
diagnostic now gets this across.

llvm-svn: 79192
This commit is contained in:
Chris Lattner 2009-08-16 16:57:27 +00:00
parent d37f61c1c6
commit 2ba5ca9d4f
3 changed files with 14 additions and 3 deletions
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3
clang/include/clang/Basic/DiagnosticSemaKinds.td
View File

@ -1687,6 +1687,9 @@ def ext_typecheck_expression_not_constant_but_accepted : Extension<
"expression is not a constant, but is accepted as one by GNU extensions">;
def warn_unused_expr : Warning<"expression result unused">,
InGroup<UnusedValue>;
def warn_unused_property_expr : Warning<
"property access result unused - getters should not have side effects">,
InGroup<UnusedValue>;
def err_incomplete_type_used_in_type_trait_expr : Error<
"incomplete type %0 used in type trait expression">;

12
clang/lib/Sema/SemaStmt.cpp
View File

@ -15,7 +15,7 @@
#include "clang/AST/APValue.h"
#include "clang/AST/ASTContext.h"
#include "clang/AST/DeclObjC.h"
#include "clang/AST/Expr.h"
#include "clang/AST/ExprObjC.h"
#include "clang/AST/StmtObjC.h"
#include "clang/AST/StmtCXX.h"
#include "clang/Basic/TargetInfo.h"
@ -65,7 +65,15 @@ void Sema::DiagnoseUnusedExprResult(const Stmt *S) {
if (!E->isUnusedResultAWarning(Loc, R1, R2))
return;
Diag(Loc, diag::warn_unused_expr) << R1 << R2;
// Okay, we have an unused result. Depending on what the base expression is,
// we might want to make a more specific diagnostic. Check for one of these
// cases now.
unsigned DiagID = diag::warn_unused_expr;
E = E->IgnoreParens();
if (isa<ObjCKVCRefExpr>(E))
DiagID = diag::warn_unused_property_expr;
Diag(Loc, DiagID) << R1 << R2;
}
Action::OwningStmtResult

2
clang/test/SemaObjC/unused.m
View File

@ -25,7 +25,7 @@ int test1(void) {
@end
void test2() {
@"pointless example call for test purposes".length; // expected-warning {{expression result unused}}
@"pointless example call for test purposes".length; // expected-warning {{property access result unused - getters should not have side effects}}
}