Bug#154767: cpp-2.95: cpp fails to parse macros with varargs correctly

[grendel@thanes.org]

Package: cpp-2.95
Version: 1:2.95.4-10
Severity: important

Given the sample code (extracted from the Linux kernel sources):

#include <stdio.h>

#define DRM_NAME "drm"
#define KERN_ERR "<7>"

#define DRM_ERROR(fmt, args...) \
        printf(KERN_ERR "[" DRM_NAME ":%s] *ERROR* " fmt , __FUNCTION__, ##
args)
        
int main()
{
    DRM_ERROR( "test\n" );
    return 0;
}

cpp produces the following code for the main() function:

int main()
{
    printf("<7>"  "[" "drm"  ":%s] *ERROR* "   "test\n"   ,  ) ;
    return 0;
}

which is incorrect according to the info docs:

   The reason for using ##' is to handle the case when args' matches
no arguments at all.  In this case, args' has an empty value.  In this
case, the second comma in the definition becomes an embarrassment: if
it got through to the expansion of the macro, we would get something
like this:

     fprintf (stderr, "success!\n" , )

which is invalid C syntax.  ##' gets rid of the comma, so we get the
following instead:

     fprintf (stderr, "success!\n")


Which is not the case. That bug breaks the compile of the 2.4.19-rc3-ac4
kernel (the DRM tree). Both cpp 3.0 and 3.1 work correctly.

-- System Information
Debian Release: testing/unstable
Kernel Version: Linux beowulf 2.4.19-rc3-ac3 #1 Sat Jul 27 21:42:48 CEST 2002 i686 unknown unknown GNU/Linux

Versions of the packages cpp-2.95 depends on:
ii  cpp                               2.95.4-15                         The GNU C preprocessor.
ii  libc6                             2.2.5-12                          GNU C Library: Shared libraries and Timezone data


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