#369 Add more Unix support from Debian Linux packaging

[yokota]

Hi Igor,

I'm working on Debian Linux to package 7-Zip.
And I adds some patches to build on some old or minor platforms.

I think these patches are also useful for others.
Please apply them.

All our patches are held on our Git at:
https://salsa.debian.org/debian/7zip/-/tree/master/debian/patches

[Igor Pavlov]

about C/7zCrc.c

+  #elif ( (defined(__clang__) && (__clang_major__ >= 3)) ||     \
+          (defined(__GNUC__)  && (__GNUC__ > 4)        )    ) && \
+        (__ARM_ARCH >= 8)

The main idea in that 7-zip's code was that we compile whole code with low __ARM_ARCH, and use
__target__("arch=armv8-a+crc") for some functions.
Then we detect CRC feature via hwcap at runtime.
So we can get single binary that will work on old and new processors, And it will use hardware CRC of new processors.
We want to get single executable that links to special "new-ISA" functions at runtime.

[yokota]

OK, so patch 0012 must be a Debian specific one.
You can drop this patch.

I will try to make more better fix in next time.

[yokota]

Hi Igor,

Thanks to appling my patch.
I make some fixup patch to 7-Zip 21.04.
Please apply it.

[Igor Pavlov]

why we can't use getauxval(AT_HWCAP) ?

[yokota]

Hi Igor,

why we can't use getauxval(AT_HWCAP) ?

Because source code stability is more important for minor platforms like kFreeBSD.

AT_HWCAP/AT_HWCAP2 values are comes from glibc source code.
https://sourceware.org/git/?p=glibc.git;a=blob;f=elf/elf.h;h=50f87bacebe3736af8c24b928e85c26dc72b449c;hb=HEAD#l1183
https://sourceware.org/git/?p=glibc.git;a=blob;f=elf/elf.h;h=50f87bacebe3736af8c24b928e85c26dc72b449c;hb=HEAD#l1205

But such wired hack often loses source code stability.
If 7-Zip works without my AT_HWCAP hack for kFreeBSD, there is no need to use AT_HWCAP.
So I revert my AT_HWCAP patch.

glibc deverolppers also discussions about similar issue .

Bug 15794 - move AT_* constants definition from elf.h into sysdeps (bits) directory
https://sourceware.org/bugzilla/show_bug.cgi?id=15794