[LLVMbugs] [Bug 2824] New: __USER_LABEL_PREFIX__ incompabitibility

[bugzilla-daemon at cs.uiuc.edu]

http://llvm.org/bugs/show_bug.cgi?id=2824

           Summary: __USER_LABEL_PREFIX__ incompabitibility
           Product: clang
           Version: unspecified
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: preprocessor
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: edwintorok at gmail.com
                CC: llvmbugs at cs.uiuc.edu


While compiling a program I got this linker error:
(.text+0x3244): undefined reference to `__USER_LABEL_PREFIX____isoc99_sscanf'

Indeed the object file contains this symbol:
$ llvm-nm client.o|grep sscanf
         U __USER_LABEL_PREFIX____isoc99_sscanf

This is the definition of sscanf (wrong):
extern int sscanf (__const char *__restrict __s, __const char *__restrict
__format, ...) __asm__ ("__USER_LABEL_PREFIX__" "__isoc99_sscanf")
__attribute__ ((__nothrow__));

This is the definition of sscanf when using gcc (or llvm-gcc) -std=c99:
extern int sscanf (__const char *__restrict __s, __const char *__restrict
__format, ...) __asm__ ("" "__isoc99_sscanf") __attribute__ ((__nothrow__));

This is the definition of sscanf if I -U __GNUC__:
extern int sscanf (const char * __s,
     const char * __format, ...) ;

Testcase:
$ cat x.c
__USER_LABEL_PREFIX__
$ gcc -E x.c
# 1 "x.c"
# 1 "<built-in>"
# 1 "<command-line>"
# 1 "x.c"

$ clang -E x.c
# 1 "x.c"
# 1 "x.c" 1
# 0 "x.c"
# 1 "<predefines>" 1
# 1 "x.c" 2
__USER_LABEL_PREFIX__


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