On Mon, Nov 09, 2020 at 02:35:58PM -0500, Jason Merrill wrote: > How about calling warn_if_unused_value instead of the new > warn_if_unused_value_p?
That seems to work if I just replace the warning_at call with warn_if_unused_value call (at least no regression in check-c++-all and libstdc++ testsuite). Initially I've tried just calling warn_if_unused_value without the NOP_EXPR stripping and code/tclass checks, but that regressed a few tests, e.g. g++.dg/warn/Wunused-14.C or c-c++-common/Wunused-var-9.c or 3 lines in the new test, e.g. because STATEMENT_LIST or CLEANUP_POINT_EXPRs would make it through and resulted in bogus warnings. 2020-11-09 Jakub Jelinek <ja...@redhat.com> PR c/97748 gcc/c-family/ * c-common.h (warn_if_unused_value): Add quiet argument defaulted to false. * c-warn.c (warn_if_unused_value): Likewise. Pass it down recursively and just return true instead of warning if it is true. Handle COMPLEX_EXPR. gcc/cp/ * cvt.c (convert_to_void): Check (complain & tf_warning) in the outer if rather than twice times in the inner one. Use warn_if_unused_value. Formatting fix. gcc/testsuite/ * c-c++-common/Wunused-value-1.c: New test. --- gcc/c-family/c-common.h.jj 2020-11-03 11:15:07.170681001 +0100 +++ gcc/c-family/c-common.h 2020-11-07 09:37:48.597233063 +0100 @@ -1362,7 +1362,7 @@ extern void warn_tautological_cmp (const tree, tree); extern void warn_logical_not_parentheses (location_t, enum tree_code, tree, tree); -extern bool warn_if_unused_value (const_tree, location_t); +extern bool warn_if_unused_value (const_tree, location_t, bool = false); extern bool strict_aliasing_warning (location_t, tree, tree); extern void sizeof_pointer_memaccess_warning (location_t *, tree, vec<tree, va_gc> *, tree *, --- gcc/c-family/c-warn.c.jj 2020-10-26 10:53:56.533885147 +0100 +++ gcc/c-family/c-warn.c 2020-11-07 09:40:51.011170825 +0100 @@ -585,7 +585,7 @@ warn_logical_not_parentheses (location_t (potential) location of the expression. */ bool -warn_if_unused_value (const_tree exp, location_t locus) +warn_if_unused_value (const_tree exp, location_t locus, bool quiet) { restart: if (TREE_USED (exp) || TREE_NO_WARNING (exp)) @@ -633,7 +633,7 @@ warn_if_unused_value (const_tree exp, lo goto restart; case COMPOUND_EXPR: - if (warn_if_unused_value (TREE_OPERAND (exp, 0), locus)) + if (warn_if_unused_value (TREE_OPERAND (exp, 0), locus, quiet)) return true; /* Let people do `(foo (), 0)' without a warning. */ if (TREE_CONSTANT (TREE_OPERAND (exp, 1))) @@ -648,6 +648,13 @@ warn_if_unused_value (const_tree exp, lo return false; goto warn; + case COMPLEX_EXPR: + /* Warn only if both operands are unused. */ + if (warn_if_unused_value (TREE_OPERAND (exp, 0), locus, true) + && warn_if_unused_value (TREE_OPERAND (exp, 1), locus, true)) + goto warn; + return false; + case INDIRECT_REF: /* Don't warn about automatic dereferencing of references, since the user cannot control it. */ @@ -671,6 +678,8 @@ warn_if_unused_value (const_tree exp, lo return false; warn: + if (quiet) + return true; return warning_at (locus, OPT_Wunused_value, "value computed is not used"); } } --- gcc/cp/cvt.c.jj 2020-07-28 15:39:09.000000000 +0200 +++ gcc/cp/cvt.c 2020-11-09 21:28:47.180254399 +0100 @@ -1568,12 +1568,13 @@ convert_to_void (tree expr, impl_conv_vo && warn_unused_value && !TREE_NO_WARNING (expr) && !processing_template_decl - && !cp_unevaluated_operand) + && !cp_unevaluated_operand + && (complain & tf_warning)) { /* The middle end does not warn about expressions that have been explicitly cast to void, so we must do so here. */ - if (!TREE_SIDE_EFFECTS (expr)) { - if (complain & tf_warning) + if (!TREE_SIDE_EFFECTS (expr)) + { switch (implicit) { case ICV_SECOND_OF_COND: @@ -1605,14 +1606,10 @@ convert_to_void (tree expr, impl_conv_vo default: gcc_unreachable (); } - } + } else { - tree e; - enum tree_code code; - enum tree_code_class tclass; - - e = expr; + tree e = expr; /* We might like to warn about (say) "(int) f()", as the cast has no effect, but the compiler itself will generate implicit conversions under some @@ -1626,21 +1623,20 @@ convert_to_void (tree expr, impl_conv_vo while (TREE_CODE (e) == NOP_EXPR) e = TREE_OPERAND (e, 0); - code = TREE_CODE (e); - tclass = TREE_CODE_CLASS (code); - if ((tclass == tcc_comparison - || tclass == tcc_unary - || (tclass == tcc_binary - && !(code == MODIFY_EXPR - || code == INIT_EXPR - || code == PREDECREMENT_EXPR - || code == PREINCREMENT_EXPR - || code == POSTDECREMENT_EXPR - || code == POSTINCREMENT_EXPR)) - || code == VEC_PERM_EXPR - || code == VEC_COND_EXPR) - && (complain & tf_warning)) - warning_at (loc, OPT_Wunused_value, "value computed is not used"); + enum tree_code code = TREE_CODE (e); + enum tree_code_class tclass = TREE_CODE_CLASS (code); + if (tclass == tcc_comparison + || tclass == tcc_unary + || (tclass == tcc_binary + && !(code == MODIFY_EXPR + || code == INIT_EXPR + || code == PREDECREMENT_EXPR + || code == PREINCREMENT_EXPR + || code == POSTDECREMENT_EXPR + || code == POSTINCREMENT_EXPR)) + || code == VEC_PERM_EXPR + || code == VEC_COND_EXPR) + warn_if_unused_value (e, loc); } } expr = build1 (CONVERT_EXPR, void_type_node, expr); --- gcc/testsuite/c-c++-common/Wunused-value-1.c.jj 2020-11-07 09:51:46.407757100 +0100 +++ gcc/testsuite/c-c++-common/Wunused-value-1.c 2020-11-07 10:15:34.295574782 +0100 @@ -0,0 +1,33 @@ +/* PR c/97748 */ +/* { dg-do compile } */ +/* { dg-options "-Wunused-value" } */ + +double _Complex f (); +double _Complex *p; + +double _Complex +foo (double _Complex x) +{ + ++x; /* { dg-bogus "value computed is not used" } */ + --x; /* { dg-bogus "value computed is not used" } */ + x += 1; /* { dg-bogus "value computed is not used" } */ + x += 1.0iF; /* { dg-bogus "value computed is not used" } */ + x++; /* { dg-bogus "value computed is not used" } */ + x--; /* { dg-bogus "value computed is not used" } */ + x + 1; /* { dg-warning "value computed is not used" } */ + (void) (x + 1); /* { dg-bogus "value computed is not used" } */ + 1 + f (); /* { dg-warning "value computed is not used" } */ + f () + f (); /* { dg-warning "value computed is not used" } */ + f () + f (), f (); /* { dg-warning "value computed is not used" } */ + f (); + (void) f (); + *p++; /* { dg-warning "value computed is not used" } */ + ++*p; /* { dg-bogus "value computed is not used" } */ + (*p ? f () : 0); + ({ f (); }); + ({ f () + 1; }); + ({ f (); 0; }); + ({ f () + 1; 0; }); /* { dg-warning "value computed is not used" } */ + 1 + ({ f (); }); /* { dg-warning "value computed is not used" } */ + return x; +} Jakub