| Message ID | 20151006172910.GS6184@redhat.com |
|---|---|
| State | New |
| Headers | show |
On 10/06/2015 11:29 AM, Marek Polacek wrote: > I've been chasing a bogus -Wtautological-compare warning that only > occurred in the C++ FE. Turned out that we were building COND_EXPRs > without a location; that means that this code in warn_tautological_cmp > didn't work as planned: > > /* Don't warn for various macro expansions. */ > if (from_macro_expansion_at (loc) > || from_macro_expansion_at (EXPR_LOCATION (lhs)) > || from_macro_expansion_at (EXPR_LOCATION (rhs))) > return; > > If we set the location properly, we're able to detect that either LHS > or RHS comes from a macro expansion. > > Bootstrapped/regtested on x86_64-linux, ok for trunk? > > 2015-10-06 Marek Polacek <polacek@redhat.com> > > PR c++/67863 > * call.c (build_conditional_expr_1): Build the COND_EXPR with > a location. > > * c-c++-common/Wtautological-compare-4.c: New test. OK. Related, I'll drop my proposed patch to builtins.c that worked around this problem. Jeff
On Tue, Oct 06, 2015 at 11:46:33AM -0600, Jeff Law wrote: > >2015-10-06 Marek Polacek <polacek@redhat.com> > > > > PR c++/67863 > > * call.c (build_conditional_expr_1): Build the COND_EXPR with > > a location. > > > > * c-c++-common/Wtautological-compare-4.c: New test. > OK. Committed. > Related, I'll drop my proposed patch to builtins.c that worked around this > problem. Yeah, thanks. Marek
diff --git gcc/cp/call.c gcc/cp/call.c index 050d045..93e28dc 100644 --- gcc/cp/call.c +++ gcc/cp/call.c @@ -5144,7 +5144,7 @@ build_conditional_expr_1 (location_t loc, tree arg1, tree arg2, tree arg3, return error_mark_node; valid_operands: - result = build3 (COND_EXPR, result_type, arg1, arg2, arg3); + result = build3_loc (loc, COND_EXPR, result_type, arg1, arg2, arg3); if (!cp_unevaluated_operand) /* Avoid folding within decltype (c++/42013) and noexcept. */ result = fold_if_not_in_template (result); diff --git gcc/testsuite/c-c++-common/Wtautological-compare-4.c gcc/testsuite/c-c++-common/Wtautological-compare-4.c index e69de29..207c401 100644 --- gcc/testsuite/c-c++-common/Wtautological-compare-4.c +++ gcc/testsuite/c-c++-common/Wtautological-compare-4.c @@ -0,0 +1,15 @@ +/* PR c++/67863 */ +/* { dg-do compile } */ +/* { dg-options "-Wtautological-compare" } */ + +extern int e; +#define A (e ? 4 : 8) +#define B (e ? 4 : 8) + +int +fn (void) +{ + if (A <= B) + return 1; + return 0; +}
I've been chasing a bogus -Wtautological-compare warning that only occurred in the C++ FE. Turned out that we were building COND_EXPRs without a location; that means that this code in warn_tautological_cmp didn't work as planned: /* Don't warn for various macro expansions. */ if (from_macro_expansion_at (loc) || from_macro_expansion_at (EXPR_LOCATION (lhs)) || from_macro_expansion_at (EXPR_LOCATION (rhs))) return; If we set the location properly, we're able to detect that either LHS or RHS comes from a macro expansion. Bootstrapped/regtested on x86_64-linux, ok for trunk? 2015-10-06 Marek Polacek <polacek@redhat.com> PR c++/67863 * call.c (build_conditional_expr_1): Build the COND_EXPR with a location. * c-c++-common/Wtautological-compare-4.c: New test. Marek