> On 7/26/22 14:58, Indu Bhagat wrote: >> On 7/22/22 4:23 AM, Jose E. Marchesi via Gcc-patches wrote: >>> >>> Contrary to CTF and our previous expectations, as per [1], turns out >>> that in BTF: >>> >>> 1) The `encoding' field in integer types shall not be treated as a >>> bitmap, but as an enumerated, i.e. these bits are exclusive to each >>> other. >>> >>> 2) The CHAR bit in `encoding' shall _not_ be set when emitting types >>> for char nor `unsigned char'. >>> >> >> Hmm...well. At this time, I suggest we make a note of this in the btf.h >> for posterity that BTF_INT_CHAR is to not be used (i.e., BTF_INT_CHAR >> should not be set for char / unsigned char). > > Agreed it would be good to add this note.
Hmm, I am not sure such a comment actually belongs to include/btf.h, which is not specific to the compiler and is supposed to reflect the BTF format per-se. The CHAR bit is documented in the kernel documentation and it may be used at some point by bpflib, or who knows what. That's why I put the comment in btfout.cc instead, to make it clear that BTF_INT_CHAR is indeed not to be set for char / unsigned char by the compiler: >>> + /* In BTF the CHAR `encoding' seems to not be used, so clear it >>> + here. */ >>> + dtd->dtd_u.dtu_enc.cte_format &= ~BTF_INT_CHAR;
