-fno-builtin breaks CHERIoT RTOS setjmp in C

[davidchisnall]

The implementation of setjmp is provided as some module-level inline assembly as a COMDAT function. If we pass -fno-builtin, then this is found in C and C++. If we do not, then C++ still finds it but C does not and then setjmp is expanded to a libcall later. I believe that we need to mark the calling convention of setjmp and longjmp as C (we currently mark all builtins as CHERI_LIBCALL).

[resistor]

Is there a test that breaks with this so I can verify the fix?

[davidchisnall]

I believe compiling a trivial .c file including our setjmp.h (or copying the code) and checking that the call to setjmp calls the defined version should work.

This triggers in the network stack, so compiling the network stack examples should validate a fix.

[rmn30]

It breaks if you remove -fno-builtin from sdk/xmake.lua with current compiler.

Ooops, wrong issue.