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Re: PR/15448: add a compiler timestamp to PCH files (take 3)



On 21/02/2005, at 4:26 AM, Theodore Papadopoulo wrote:


On Sat, 2005-02-19 at 18:58 -0800, Geoff Keating wrote:
The proper solution is to implement a validation check that actually
does check that the executable is the same.  For instance, create a
small C file that contains a checksum of the executable, initially
all
zeros, and link (possibly with -s to strip) the executable with that
file; then checksum the result, create a new C file that has the
correct checksum, and link again.  (You could avoid the double link,
but doing so portably would be inelegant, and linking doesn't take
very
long.)

Why not simply generate a md5sum of all the relevant compiler source files as a magic number and integrate that into the PCH file. Surely an overkill that is much more strict than necessary (any comment change will affect the number), but simple, very fast both at write and read times, compact and sure...

Because that doesn't cover everything, and we already have quite enough half-solutions for the problem.

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