https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116806
Bug ID: 116806
Summary: gcc.dg/cpp/charconst-3.c breakage on 16-bit targets
Product: gcc
Version: 14.2.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: testsuite
Assignee: unassigned at gcc dot gnu.org
Reporter: mikpelinux at gmail dot com
Target Milestone: ---
The following is adapted from gcc.dg/cpp/charconst-3.c:
==snip==
void foo (int);
void __attribute__ ((__noreturn__)) _exit (int);
#define A '\234b'
#define B ((int) ((unsigned char) '\234' * scale + (unsigned char) 'b'))
int main (void)
{
int scale = 256;
foo (A);
foo (B);
if (A != B)
_exit (1);
return 0;
}
==snip==
Compiling this for a 16-bit target shows that (1) A and B evaluate to the same
runtime value, but (2) the two are statically considered to be different
causing an unconditional call to _exit.
Taking xstormy16 as an example, this is what gcc-14.2 generates for main:
main:
mov.w r2,#-25502
callf foo
mov.w r2,#-25502
callf foo
mov.w r2,#1
callf _exit
i.e., the values are the same yet somehow different. Other 16-bit targets show
the exact same pattern (tested avr, msp430, pdp11, rl78, and xstormy16).
Compiling for x86-64 shows different behaviour:
main:
.LFB0:
.cfi_startproc
pushq %rax
.cfi_def_cfa_offset 16
movl $40034, %edi
call foo
movl $40034, %edi
call foo
xorl %eax, %eax
popq %rdx
.cfi_def_cfa_offset 8
ret
A and B still evaluate to the same runtime value, but this time gcc realizes
this and does not emit a call to _exit.
Found when debugging this test case on an out-of-tree port to a 16-bit target.
