https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126068
Bug ID: 126068
Summary: Empty second operand to the conditional operator in
the preprocessor
Product: gcc
Version: 16.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: [email protected]
Target Milestone: ---
I don't see a good reason to disallow the compact version of the conditional
operator in the preprocessor. This bug was reported by a C Committee member
while reviewing n3905, which attempts to standardize this feature.
alx@devuan:~/tmp$ cat pp.c
#if defined(X) ? 1 : 0
# warning a
#else
# warning b
#endif
#if defined(X) ?: 0
# error a
#else
# error b
#endif
alx@devuan:~/tmp$ gcc pp.c
pp.c:4:3: warning: #warning b [-Wcpp]
4 | # warning b
| ^~~~~~~
pp.c:7:17: error: operator ‘?’ has no right operand
7 | #if defined(X) ?: 0
| ^
pp.c:10:3: error: #error b
10 | # error b
| ^~~~~
alx@devuan:~/tmp$ gcc -DX pp.c
pp.c:2:3: warning: #warning a [-Wcpp]
2 | # warning a
| ^~~~~~~
pp.c:7:17: error: operator ‘?’ has no right operand
7 | #if defined(X) ?: 0
| ^
pp.c:10:3: error: #error b
10 | # error b
| ^~~~~
