Avoid "cc1: warning: is shorter than expected" when using GNU cpp in

combination with dtrace scripts, which have "#!/usr/sbin/dtrace -Cs"
shebang lines.  This is because dtrace positions the file pointer after
the shebang line, before passing the file to GNU cpp.

To fix the warning, adjust the size downwards by the current position,
after a bit of sanity checking.

Suggested by:	avg
MFC after:	1 week

1 files changed, 16 insertions, 0 deletions

diff --git a/contrib/gcclibs/libcpp/files.c b/contrib/gcclibs/libcpp/files.c
index 0e9f977..366d30a 100644
--- a/contrib/gcclibs/libcpp/files.c
+++ b/contrib/gcclibs/libcpp/files.c
@@ -546,6 +546,7 @@ static bool
 read_file_guts (cpp_reader *pfile, _cpp_file *file)
 {
   ssize_t size, total, count;
+  off_t offset;
   uchar *buf;
   bool regular;
 
@@ -573,6 +574,21 @@ read_file_guts (cpp_reader *pfile, _cpp_file *file)
 	}
 
       size = file->st.st_size;
+
+      if ((offset = lseek(file->fd, 0, SEEK_CUR)) < 0)
+	{
+	  cpp_error (pfile, CPP_DL_ERROR, "%s has no current position",
+	    file->path);
+	  return false;
+	}
+      else if (offset > INTTYPE_MAXIMUM (ssize_t) || (ssize_t)offset > size)
+	{
+	  cpp_error (pfile, CPP_DL_ERROR, "current position of %s is too large",
+	    file->path);
+	  return false;
+	}
+
+      size -= (ssize_t)offset;
     }
   else
     /* 8 kilobytes is a sensible starting size.  It ought to be bigger