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Re: stray warning from gcc's cpp


on 19/03/2014 12:03 Andriy Gapon said the following:
> 
> I observe the following minor annoyance on FreeBSD systems where cpp is GCC's
> cpp.  If a DTrace script has the following shebang line:
> #!/usr/sbin/dtrace -Cs
> then the following warning is produced when the script is run:
> cc1: warning:  is shorter than expected
> 
> Some details.  dtrace(1) first forks. Then a child seeks on a file descriptor
> associated with the script file, so that the shebang line is skipped (because
> otherwise it would confuse cpp).  Then the child makes the file descriptor its
> standard input and then it execs cpp.  cpp performs fstat(2) on its standard
> input descriptor and determines that it points to a regular file.  Then it
> verifies that a number of bytes it reads from the file is the same as a size of
> the file.  The check makes sense if the file is opened by cpp itself, but it
> does not always make sense for the stdin as described above.
> 
> The following patch seems to fix the issue, but perhaps there is a better /
> smarter alternative.

A patch that implements a different approach has been committed in FreeBSD:
https://github.com/freebsd/freebsd/commit/6ceec4444ddbc
Please consider.  Thanks!

> --- a/libcpp/files.c
> +++ b/libcpp/files.c
> @@ -601,7 +601,8 @@ read_file_guts (cpp_reader *pfile, _cpp_file *file)
>        return false;
>      }
> 
> -  if (regular && total != size && STAT_SIZE_RELIABLE (file->st))
> +  if (regular && total != size && file->fd != 0
> +      && STAT_SIZE_RELIABLE (file->st))
>      cpp_error (pfile, CPP_DL_WARNING,
>  	       "%s is shorter than expected", file->path);
> 
> 


-- 
Andriy Gapon


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