http://llvm.org/bugs/show_bug.cgi?id=19649
Bug ID: 19649
Summary: glibc exposed issue: wide character literal fails to
behave as literal of its underlying type in
preprocessor conditions
Product: clang
Version: 3.4
Hardware: Other
OS: Linux
Status: NEW
Severity: normal
Priority: P
Component: Frontend
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected]
Classification: Unclassified
Certain versions of glibc use conditional inclusion to decide on the definition
of WCHAR_MIN. Clang picks the wrong definition.
According to C99 subclause 6.4.4.4 paragraph 11:
A wide character constant has type wchar_t, an integer type defined in the
<stddef.h> header.
The following source demonstrates that Clang will not treat a wide character
constant in the controlling expression of a preprocessing directive for
conditional inclusion in a way that is consistent with the above.
In particular, wchar_t is a synonym for int on the system in question (as
shown).
L'\0' does not behave consistently with 0 although both have the same type.
### SOURCE:> cat wchar_tPlay.c
extern __typeof__(L'\0') wchar;
extern int wchar;
#if (L'\0' - 1 < 0) != (0 - 1 < 0)
# warning
#endif
Return: 0x00:0
### COMPILER INVOCATION AND OUTPUT:> clang -std=c99 wchar_tPlay.c -c
wchar_tPlay.c:5:3: warning: [-W#warnings]
# warning
^
1 warning generated.
Return: 0x00:0
### VERSION INFO:> clang -v
clang version 3.4 (tags/RELEASE_34/final)
Target: powerpc64-unknown-linux-gnu
Thread model: posix
Found candidate GCC installation: /usr/lib/gcc/ppc64-redhat-linux/4.4.4
Found candidate GCC installation: /usr/lib/gcc/ppc64-redhat-linux/4.4.6
Selected GCC installation: /usr/lib/gcc/ppc64-redhat-linux/4.4.6
Return: 0x00:0
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