Starting with revision 206620, if we have LHS op= RHS and RHS has
side effects, we preevaluate RHS first, which means that we wrap it
in C_MAYBE_CONST_EXPR_EXPR + SAVE_EXPR. This regressed -Wconversion,
since we now issue bogus warnings. The reason is that conversion_warning
doesn't grok C_MAYBE_CONST_EXPR_EXPR/SAVE_EXPR, meaning that it
just calls unsafe_conversion_p on it that warns. But for e.g. relational
and equality operators that's useless as those always yield 0 or 1.
This patch fixes this by unwrapping the expr first.
Regtested/bootstrapped on x86_64-linux, ok for trunk?
2014-02-04 Marek Polacek <pola...@redhat.com>
PR c/60036
c-family/
* c-common.c (conversion_warning): Unwrap C_MAYBE_CONST_EXPR and/or
SAVE_EXPR.
testsuite/
* gcc.dg/pr60036.c: New test.
diff --git gcc/c-family/c-common.c gcc/c-family/c-common.c
index fc12788..007e727 100644
--- gcc/c-family/c-common.c
+++ gcc/c-family/c-common.c
@@ -2714,6 +2714,14 @@ conversion_warning (location_t loc, tree type, tree expr)
if (!warn_conversion && !warn_sign_conversion && !warn_float_conversion)
return;
+ /* This may happen, because for LHS op= RHS we preevaluate
+ RHS and create C_MAYBE_CONST_EXPR <SAVE_EXPR <RHS>>, which
+ means we could no longer see the code of the EXPR. */
+ if (TREE_CODE (expr) == C_MAYBE_CONST_EXPR)
+ expr = C_MAYBE_CONST_EXPR_EXPR (expr);
+ if (TREE_CODE (expr) == SAVE_EXPR)
+ expr = TREE_OPERAND (expr, 0);
+
switch (TREE_CODE (expr))
{
case EQ_EXPR:
diff --git gcc/testsuite/gcc.dg/pr60036.c gcc/testsuite/gcc.dg/pr60036.c
index e69de29..07eb6ac 100644
--- gcc/testsuite/gcc.dg/pr60036.c
+++ gcc/testsuite/gcc.dg/pr60036.c
@@ -0,0 +1,28 @@
+/* PR c/60036 */
+/* { dg-do compile } */
+/* { dg-options "-Wconversion" } */
+
+extern int fn (void);
+
+void
+foo (int i)
+{
+ unsigned int f = 9;
+
+ /* Don't warn on these. */
+ f += fn () || i;
+ f += fn () && i;
+ f += ! fn ();
+ f -= fn () == i;
+ f |= fn () != i;
+ f &= fn () < i;
+ f ^= fn () > i;
+ f &= fn () <= i;
+ f ^= fn () >= i;
+
+ /* But warn on the following. */
+ f += fn (); /* { dg-warning "conversion" } */
+ f += fn () | i; /* { dg-warning "conversion" } */
+ f += fn () & i; /* { dg-warning "conversion" } */
+ f += fn () ^ i; /* { dg-warning "conversion" } */
+}
Marek
