[bregma]

You should read ISO/IEC 8859:2011 J.5.10 "The asm keyword". It's the same section in the C18 standard. It's the bit describing the way an ISO C certified compiler shall provide inline assembly.

[pjmlp]

I am fully aware of it, it clearly specifies that it is implementation specific.

Two C certified compilers for the same platform are free to provide completely different behaviours for what asm is supposed to do.

Anyone that cares about compilers does actually read ISO documents.