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源代码在线查看： c99-const-expr-3.c
/* Test for constant expressions: broken optimization with const variables. */ /* Origin: Joseph Myers */ /* { dg-do compile } */ /* { dg-options "-std=iso9899:1999 -O2" } */ /* Note: not using -pedantic since the -std option alone should be enough to give the correct behavior to conforming programs. */ static const int ZERO = 0; static const double DZERO = 0; int *a; int b; long *c; /* Assertion that n is a constant zero: so the conditional expression has type 'int *' instead of 'void *'. */ #define ASSERT_NPC(n) (b = *(1 ? a : (n))) /* Assertion that n is not a constant zero: so the conditional expressions has type 'void *' instead of 'int *'. */ #define ASSERT_NOT_NPC(n) (c = (1 ? a : (void *)(__SIZE_TYPE__)(n))) void foo (void) { ASSERT_NPC (0); ASSERT_NOT_NPC (ZERO); ASSERT_NPC (0 + 0); ASSERT_NOT_NPC (ZERO + 0); /* { dg-bogus "incompatible" "bogus null pointer constant" { xfail *-*-* } } */ ASSERT_NOT_NPC (ZERO + ZERO); /* { dg-bogus "incompatible" "bogus null pointer constant" { xfail *-*-* } } */ ASSERT_NPC (+0); ASSERT_NOT_NPC (+ZERO); /* { dg-bogus "incompatible" "bogus null pointer constant" { xfail *-*-* } } */ ASSERT_NPC (-0); ASSERT_NOT_NPC (-ZERO); /* { dg-bogus "incompatible" "bogus null pointer constant" { xfail *-*-* } } */ ASSERT_NPC ((char) 0); ASSERT_NOT_NPC ((char) ZERO); ASSERT_NPC ((int) 0); ASSERT_NOT_NPC ((int) ZERO); ASSERT_NPC ((int) 0.0); ASSERT_NOT_NPC ((int) DZERO); ASSERT_NOT_NPC ((int) +0.0); /* { dg-bogus "incompatible" "bogus null pointer constant" { xfail *-*-* } } */ ASSERT_NOT_NPC ((int) (0.0+0.0)); /* { dg-bogus "incompatible" "bogus null pointer constant" { xfail *-*-* } } */ ASSERT_NOT_NPC ((int) (double)0.0); /* { dg-bogus "incompatible" "bogus null pointer constant" { xfail *-*-* } } */ }
