Re: Is CPP broken? (Re: Strange gcc error message)

[Neil Booth <neil at daikokuya dot demon dot co dot uk>]

H . J . Lu wrote:-

> In open_file (),
> 
>           /* Mark a regular, zero-length file never-reread now.  */
>           if (S_ISREG (file->st.st_mode) && file->st.st_size == 0)
>             {       
>               _cpp_never_reread (file); 
>               close (file->fd);
>               file->fd = -1;
>             }
> 
>           return file;

I've taken an approach suggested by Zack in a private mail.  We still
mark zero-length files not to be reread, but push a buffer of length
zero the first time.  This means moving the above code fragment out of
open_file(), and doing the flagging in stack_include_file after
committing to pushing the file once.

The patch below bootstraps without regressions (I think - it's a bit
of a mess right now, particularly ObjC).  I've checked that your example
issues no diagnostics and that the exit code is 0.

I also solved another issue that Zack pointed out: we would sometimes
issue a diagnostic twice (e.g. permission denied if the file were not
readable).

Unfortunately, I have no idea how to test for these things with
DejaGnu.

Neil.

	* cppfiles.c (open_file): Don't mark zero-length files
	never-reread here.  Don't output diagnostics here either.
	(stack_include_file): Mark them never-reread here.
	(_cpp_read_file): Update.

Index: cppfiles.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/cppfiles.c,v
retrieving revision 1.129
diff -u -p -r1.129 cppfiles.c
--- cppfiles.c	2001/08/22 20:37:17	1.129
+++ cppfiles.c	2001/10/08 06:52:59
@@ -248,30 +248,15 @@ open_file (pfile, filename)
 
   if (file->fd != -1 && fstat (file->fd, &file->st) == 0)
     {
+      if (!S_ISDIR (file->st.st_mode))
+	return file;
       /* If it's a directory, we return null and continue the search
 	 as the file we're looking for may appear elsewhere in the
 	 search path.  */
-      if (S_ISDIR (file->st.st_mode))
-	errno = ENOENT;
-      else
-	{
-	  /* Mark a regular, zero-length file never-reread now.  */
-	  if (S_ISREG (file->st.st_mode) && file->st.st_size == 0)
-	    {
-	      _cpp_never_reread (file);
-	      close (file->fd);
-	      file->fd = -1;
-	    }
-
-	  return file;
-	}
+      errno = ENOENT;
     }
 
-  /* Don't issue an error message if the file doesn't exist.  */
   file->err_no = errno;
-  if (errno != ENOENT && errno != ENOTDIR)
-    cpp_error_from_errno (pfile, file->name);
-
   return 0;
 }
 
@@ -302,9 +287,14 @@ stack_include_file (pfile, inc)
   /* Not in cache?  */
   if (! inc->buffer)
     {
-      /* If an error occurs, do not try to read this file again.  */
-      if (read_include_file (pfile, inc))
+      /* Mark a regular, zero-length file never-reread.  Zero-length
+	 files are stacked the first time, so preprocessing a main
+	 file of zero length does not raise an error.  */
+      if (S_ISREG (inc->st.st_mode) && inc->st.st_size == 0)
+	_cpp_never_reread (inc);
+      else if (read_include_file (pfile, inc))
 	{
+	  /* If an error occurs, do not try to read this file again.  */
 	  _cpp_never_reread (inc);
 	  return false;
 	}
@@ -710,14 +700,14 @@ _cpp_read_file (pfile, fname)
      const char *fname;
 {
   struct include_file *f = open_file (pfile, fname);
-  bool stacked = false;
 
   if (f == NULL)
-    cpp_error_from_errno (pfile, fname);
-  else
-    stacked = stack_include_file (pfile, f);
+    {
+      cpp_error_from_errno (pfile, fname);
+      return false;
+    }
 
-  return stacked;
+  return stack_include_file (pfile, f);
 }
 
 /* Do appropriate cleanup when a file buffer is popped off the input