libucontext-1.4 fails to build with clang

[Biswa96]

libucontext-1.4 fails to build for i686, arm and x86_64 with clang targeting Android system. Full build log can be found here https://github.com/termux/termux-packages/actions/runs/20125553514

Here are the compiler errors.

• arm

 ../src/arch/arm/swapcontext.S:27:11: error: unknown token in expression
 ldr r2, =#0x56465001
          ^
../src/arch/arm/getcontext.S:34:13: error: unknown token in expression
 ldrne r2, =#0x56465001
            ^

• i686

 ../src/arch/x86/makecontext.c:39:55: error: subscripted value is not an array, pointer, or vector
   39 |         ucp->uc_mcontext.fpregs = (void *) &ucp->__fpregs_mem[0];
      |                                             ~~~~~~~~~~~~~~~~~^~

• x86_64

 ../src/arch/x86_64/makecontext.c:39:55: error: subscripted value is not an array, pointer, or vector
   39 |         ucp->uc_mcontext.fpregs = (void *) &ucp->__fpregs_mem[0];
      |                                             ~~~~~~~~~~~~~~~~~^~

[robertkirkman]

I'm able to reproduce a very similar error when attempting to build libucontext on 32-bit x86 GNU/Linux with both GCC and Clang and with both -Dfreestanding=true and -Dfreestanding=false, I have posted my log in the linked other thread.

[kaniini]

The x86/x86-64 builds were due to a difference in bionic's headers: they store the FPR memory block as a structure, while both glibc and musl use a raw block of memory instead.

ARM issue appears to be with clang's assembler, investigating a fix for that.

[kaniini]

This was fixed by 76f6755