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Re: PCH not being used, but I can't tell why

On Mon, Aug 11, 2003 at 05:16:51PM -0700, Geoff Keating wrote:
> It should be being called from validate_pch in cppfiles.c (as
> "cb.valid_pch"), right above where the line with the 'x' is printed.
> The only way it wouldn't be called is if open_file had earlier
> returned 'false'.  Could you see if that's really happening, and if so
> why open_file is doing that?

Because open_file was passed "." followed by ".." before ever getting to
an actual file.

    if (open_file (file))
          happy things
      file->pch = 2;  // 2 == "is not and can never be a valid pch file"

The first attempt to open the .pch file actually finds the .gch directory,
which then causes a readdir loop, passing each entry to validate_pch,
but 1) not skipping the pointless directory entries, and 2) not clearing
the pch flag in each loop.

So, the first probe on "." sets pch = 2, and it's never reset, only examined.
The rest of the logic relies on (or assumes) that 'file' won't be referring
to a series of difference files, which is false here.

Applying the patch below gives me this:

cc1plus: warning: /mnt/build/build-2003-08-11/i686-pc-linux-gnu/libstdc++-v3/include/i686-pc-linux-gnu/bits/stdc++.h.gch/O0g: not used because `__tune_i686__' not defined
cc1plus: warning: /mnt/build/build-2003-08-11/i686-pc-linux-gnu/libstdc++-v3/include/i686-pc-linux-gnu/bits/stdc++.h.gch/O2g: not used because `__tune_i686__' not defined

...whatever the fsck that means.

Resetting the pch status flag seems necessary.  The skipping of "." and
".." isn't needed for correctness as long as the flag is reset, but it does
speed things up a tad.  I don't know cpplib, maybe there's some abstracted
test that should be used instead of strcmp against string literals, but
this is the essence of what needs to be done in pch_open_file():

Index: cppfiles.c
RCS file: /home/pme/Repositories/GCC/gcc/gcc/cppfiles.c,v
retrieving revision 1.186
diff -u -p -r1.186 cppfiles.c
--- cppfiles.c	9 Aug 2003 22:14:07 -0000	1.186
+++ cppfiles.c	12 Aug 2003 06:08:09 -0000
@@ -273,12 +273,16 @@ pch_open_file (cpp_reader *pfile, _cpp_f
 	  while ((d = readdir (pchdir)) != NULL)
 	      dlen = strlen (d->d_name) + 1;
+	      if ((strcmp (d->d_name, ".") == 0)
+		  || (strcmp (d->d_name, "..") == 0))
+		continue;
 	      if (dlen + plen > len)
 		  len += dlen + 64;
 		  pchname = xrealloc (pchname, len);
 	      memcpy (pchname + plen, d->d_name, dlen);
+	      file->pch = 0;
 	      valid = validate_pch (pfile, file, pchname);
 	      if (valid)

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