Re: Portability: common-src/amcrc32chw.c & config/amanda/amanda_configure.m4

I was able to successfully compile using the attached patch.


Jean-Louis Martineau writes:
- On 03/01/17 05:14 PM, Eric Schnoebelen wrote:
- > Jean-Louis Martineau writes:
- > - amanda detect at run time if the sse4.2 instruction are available and
- > - use them only if they are available.
- > - different code is used if the sse4.2 instruction are not available.
- > - What's wrong with that?
- >
- > Backing up.
- >
- > The original code *assumed* that if you were using GCC and it
- > was at least 4.3 on any x86 processor architecture, the
- > __builtin_ia32_* functions would be available.
- >
- > However, as you've stated, that is only true if the compliler is
- > called with the ``-msse4.2'' (or other -msse* flags?).
- >
- > And amanda *assumed* it was being compiled with the ``-msse4.2''
- > (or similar) flag.
-
- That's the problem, you removed the flag
-
- > pkgsrc explicitly strips such flags from compile tests for
- > maximal portability for it's binary builds across systems.
-
- As I already said, even if the binary have sse4.2 instructions, they are=20
- executed only if the CPU have it, there is a runtime check for there=20
- availability.
-
- >
- > Given that gcc wasn't given ``-msse4.2'' on the complile/load
- > command line, the __builtin_ia32_* functions were unable to be
- > resolved at link time.
- >
- > Summary: amanda was blindly using (builtin) library routines
- > with out insuring that they were resolvable at compile/link
- > time.  My original patch at least tested for their existence and
- > didn't try to use that code path if a compile test for the
- > functions failed.
-
- Your patch never detected them.
-
- >
- > - If I understand, you want an option to completely disable sse4.2?
- > - You do not want newer CPU to use sse4.2
- > - I don't understand since amanda detect sse4.2 at run time.
- >
- > See above about amanda in pkgsrc not getting the compile time
- > compiler flag detection.
- >
- > Effectively, pkgsrc isn't allowing the ``-msse4.2'' flag through
- > to the test cases to expose the associated builtins.
- >