On Wed, Jun 03, 2015 at 06:02:12PM +0000, Joseph Myers wrote: > I'm not clear on what trees you get in the problem case (or which of the > tests in the testcase you added was broken before - they don't seem that > similar to the tests in the bug). It would seem safer to me to use > lvalue_p (value) as the condition for adding a NON_VALUE_EXPR.
E.g. int *p; (int *) (char *) p = 0; wasn't rejected before. In this case build_c_cast tried to cast "(char *) p", which is a NOP_EXPR, to "(int *)". There's this value = convert (type, value); which trims the NOP_EXPR and we get "p". Then there's if (value == expr) value = non_lvalue_loc (loc, value); but that's false since it's comparing "p" and "(char *) p", so we don't wrap the "p" in NON_VALUE_EXPR. Hopefully this makes the issue a tad clearer. Using lvalue_p is fine as well, so adjusted. > That's not a cast to a qualified type. A cast to qualified type would be > (int *const) p. Duh, adjusted. Thanks. Bootstrapped/regtested on x86_64-linux pending, ok if it passes? 2015-06-03 Marek Polacek <pola...@redhat.com> PR c/66341 * c-typeck.c (build_c_cast): Wrap VALUE into NON_LVALUE_EXPR if it is a lvalue. * gcc.dg/lvalue-8.c: New test. diff --git gcc/c/c-typeck.c gcc/c/c-typeck.c index f55d4c6..6b313f3 100644 --- gcc/c/c-typeck.c +++ gcc/c/c-typeck.c @@ -5195,7 +5195,7 @@ build_c_cast (location_t loc, tree type, tree expr) } /* Don't let a cast be an lvalue. */ - if (value == expr) + if (lvalue_p (value)) value = non_lvalue_loc (loc, value); /* Don't allow the results of casting to floating-point or complex diff --git gcc/testsuite/gcc.dg/lvalue-8.c gcc/testsuite/gcc.dg/lvalue-8.c index e69de29..04eeb71 100644 --- gcc/testsuite/gcc.dg/lvalue-8.c +++ gcc/testsuite/gcc.dg/lvalue-8.c @@ -0,0 +1,19 @@ +/* PR c/66341 */ +/* { dg-do compile } */ + +void +foo (int *p) +{ + p = 0; + /* A cast does not yield an lvalue. */ + (int *) p = 0; /* { dg-error "lvalue required as left operand of assignment" } */ + /* A cast to a qualified type has the same effect as a cast + to the unqualified version of the type. */ + (int *const) p = 0; /* { dg-error "lvalue required as left operand of assignment" } */ + (int *) (char *) p = 0; /* { dg-error "lvalue required as left operand of assignment" } */ + (int *) (char *) (int *) p = 0; /* { dg-error "lvalue required as left operand of assignment" } */ + (int *) (char *) (int *) (char *) p = 0; /* { dg-error "lvalue required as left operand of assignment" } */ + (int *) (double *) p = 0; /* { dg-error "lvalue required as left operand of assignment" } */ + (int *) (int *) p = 0; /* { dg-error "lvalue required as left operand of assignment" } */ + (int *) (int *const) p = 0; /* { dg-error "lvalue required as left operand of assignment" } */ +} Marek