[PATCH] w32: Use __declspec(thread) for FIPS thread context TLS

[NIIBE Yutaka]

Hello,

Martin Storsjö <martin at martin.st> wrote:
> With the upcoming GCC 16, it should be possible to use the Windows native 
> TLS mechanism with GCC as well - but this is a choice that is made when 
> GCC is configured and built; the syntax used for declaring the variable as 
> thread local does not affect it.

Thanks for the information.  I didn't know that GCC 16 will come with
possible Windows native TLS mechanism.

The issue here is how TLS (by C language) works on Windows, and there
are multiple ways.

IIUC, by changing the code to "__declspec(thread)", it becomes
non-thread-local (equivalent to remove "__thread"), hence, the problem
of linkage at runtime looks gone superficially.  As long as an
application is not multi-threaded or it doesn't care about FIPS
certification, it's OK.  It might be a workaround in some situations.

I think that it is the decision of a user who builds libgcrypt with
whatever compiler with whatever options, until compilers with TLS
stabilized.

In the current situation (where thread local strage implementations
differ among compilrs+compiler-options), a user should be careful about
consequences like dependency to runtime libraries.

If really needed, I'm open to introduce new code for Windows, using
Windows native TLS mechanism in fips.c.

I believe that the situation is better for POSIX systems.
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