Problems bootstrapping mainline on cygwin: warning: ./cc1-checksum.o ./cc1obj-checksum.o ./cc1plus-checksum.o libgcc/_chkstk.o differ

Problems bootstrapping mainline on cygwin: warning: ./cc1-checksum.o ./cc1obj-checksum.o ./cc1plus-checksum.o libgcc/_chkstk.o differ

[Christian Joensson]

I haven't bootstrapped gcc on cygwin for a while now... but, using gcc cvs trunk
LAST_UPDATED: Fri Aug  5 09:05:37 UTC 2005, I get comparison warnings...:

warning: ./cc1-checksum.o differs
warning: ./cc1obj-checksum.o differs
warning: ./cc1plus-checksum.o differs

what does that mean?? the compare passes... and the build continues...

---
Cheers,

/ChJ

Re: Problems bootstrapping mainline on cygwin: warning: ./cc1-checksum.o ./cc1obj-checksum.o ./cc1plus-checksum.o libgcc/_chkstk.o differ

[James E Wilson]

Christian Joensson wrote:
> warning: ./cc1-checksum.o differs
> warning: ./cc1obj-checksum.o differs
> warning: ./cc1plus-checksum.o differs
> what does that mean?? the compare passes... and the build continues...

The checksums are used for PCH validatation.  We generate md5 checksums 
for each cc1 binary, write them into the PCH files, and then check them 
when reading PCH files to make sure the right PCH files are used with 
the right compiler binaries.

If the checksums differ, then this could be an assembler/linker issue 
for the target that makes it difficult to generate repeatable checksums 
of executable files during a bootstrap, or it could mean a portability 
problem with the code that generates the checksums.  It does not mean a 
compiler code generation error.  Hence it is a warning instead of an 
error that stops the bootstrap.

See the checksum related rules in the Makefile, and the genchecksum.c file.
-- 
Jim Wilson, GNU Tools Support, http://www.specifix.com

Re: Problems bootstrapping mainline on cygwin: warning: ./cc1-checksum.o ./cc1obj-checksum.o ./cc1plus-checksum.o libgcc/_chkstk.o differ

[Danny Smith]

Christian Joensson wrote

> I haven't bootstrapped gcc on cygwin for a while now... but, using gcc
> cvs trunk LAST_UPDATED: Fri Aug 5 09:05:37 UTC 2005, I get comparison
> warnings...:

> warning: ./cc1-checksum.o differs
> warning: ./cc1obj-checksum.o differs
> warning: ./cc1plus-checksum.o differs

ld inserts an 4 byte timestamp into the "Image File Header" (offset 4
bytes) of pe-coff executables. I believe that genchecksum.c takes that
into account at line 46:

 /* Some executable formats have timestamps in the first 16 bytes, yuck.  */
  if (fseek (f, 16, SEEK_SET) != 0)

But ld also inserts a 4-byte checksum of its own further down, (offset
64 bytes into the Image Optional Header).  Changes in timestamps between
stages will cause changes in the Optional Header checksums. GCC's
genchecksum doesn't take that into account.

I'd  guess that the checksum diff for libgcc/_chkstk.o is due to
differences in the name of the preprocessor-generated temp *.s
assembly file in .stabstr section

Danny

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