https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67863
Bug ID: 67863
Summary: -Wtautological-compare warns when it shouldn't
Product: gcc
Version: 6.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: mpolacek at gcc dot gnu.org
Target Milestone: ---
extern int e;
#define A (e ? 4 : 8)
#define B (e ? 4 : 8)
int
fn (void)
{
if (A <= B)
return 1;
return 0;
}
cc1plus warns, while cc1 does not. What happens here is that the COND_EXPRs
warn_tautological_cmp gets don't have a location in cc1plus:
(gdb) pt
warning: Expression is not an assignment (and might have no effect)
<cond_expr 0x7ffff16fa990
type <integer_type 0x7ffff16ff7e0 int public SI
size <integer_cst 0x7ffff171d0a8 constant 32>
unit size <integer_cst 0x7ffff171d0c0 constant 4>
align 32 symtab 0 alias set -1 canonical type 0x7ffff16ff7e0 precision
32 min <integer_cst 0x7ffff171d060 -2147483648> max <integer_cst 0x7ffff171d078
2147483647>
pointer_to_this <pointer_type 0x7ffff1721930>>
arg 0 <ne_expr 0x7ffff1853cd0
type <boolean_type 0x7ffff16ffd20 bool public unsigned QI
size <integer_cst 0x7ffff16fbf48 constant 8>
unit size <integer_cst 0x7ffff16fbf60 constant 1>
align 8 symtab 0 alias set -1 canonical type 0x7ffff16ffd20
precision 1 min <integer_cst 0x7ffff171d1b0 0> max <integer_cst 0x7ffff171d1e0
1>>
arg 0 <var_decl 0x7ffff1707bd0 e type <integer_type 0x7ffff16ff7e0 int>
used public external decl_2 SI file b.c line 1 col 12 size
<integer_cst 0x7ffff171d0a8 32> unit size <integer_cst 0x7ffff171d0c0 4>
align 32 context <translation_unit_decl 0x7ffff7ff91e0 D.1> chain
<function_decl 0x7ffff1854c40 __cxa_call_unexpected>>
arg 1 <integer_cst 0x7ffff171d1f8 constant 0>>
arg 1 <integer_cst 0x7ffff171d588 type <integer_type 0x7ffff16ff7e0 int>
constant 4>
arg 2 <integer_cst 0x7ffff186ac30 type <integer_type 0x7ffff16ff7e0 int>
constant 8>>
in cc1:
(gdb) pt
warning: Expression is not an assignment (and might have no effect)
<cond_expr 0x7ffff1828b70
type <integer_type 0x7ffff16ff7e0 int public SI
size <integer_cst 0x7ffff16fbee8 constant 32>
unit size <integer_cst 0x7ffff16fbf00 constant 4>
align 32 symtab 0 alias set -1 canonical type 0x7ffff16ff7e0 precision
32 min <integer_cst 0x7ffff16fbea0 -2147483648> max <integer_cst 0x7ffff16fbeb8
2147483647>
pointer_to_this <pointer_type 0x7ffff1719930>>
arg 0 <ne_expr 0x7ffff182b050 type <integer_type 0x7ffff16ff7e0 int>
arg 0 <c_maybe_const_expr 0x7ffff182b028 type <integer_type
0x7ffff16ff7e0 int>
arg 1 <var_decl 0x7ffff1707c60 e>>
arg 1 <integer_cst 0x7ffff1718048 constant 0>
b.c:8:7>
arg 1 <integer_cst 0x7ffff1718330 type <integer_type 0x7ffff16ff7e0 int>
constant 4>
arg 2 <integer_cst 0x7ffff18191e0 type <integer_type 0x7ffff16ff7e0 int>
constant 8>
b.c:8:7>
