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The following is an example, >> $ cat t.c >> signed char a; >> char b; >> $ clang -O2 -g -c t.c >> $ pahole -JV t.o >> ... >> [1] INT signed char size=1 nr_bits=8 encoding=(none) >> [2] INT char size=1 nr_bits=8 encoding=(none) >> In the above encoding '(none)' implies unsigned type. >> >> But if the same program is compiled with bpf target, >> $ clang -target bpf -O2 -g -c t.c >> $ bpftool btf dump file t.o >> [1] INT 'signed char' size=1 bits_offset=0 nr_bits=8 encoding=SIGNED >> [2] VAR 'a' type_id=1, linkage=global >> [3] INT 'char' size=1 bits_offset=0 nr_bits=8 encoding=SIGNED >> [4] VAR 'b' type_id=3, linkage=global >> [5] DATASEC '.bss' size=0 vlen=2 >> type_id=2 offset=0 size=1 (VAR 'a') >> type_id=4 offset=0 size=1 (VAR 'b') >> the 'char' and 'signed char' are encoded as SIGNED integers. >> >> Encode 'char' and 'signed char' as SIGNED should be a right to >> do and it will be consistent with bpf implementation. >> >> With this patch, >> $ pahole -JV t.o >> ... >> [1] INT signed char size=1 nr_bits=8 encoding=SIGNED >> [2] INT char size=1 nr_bits=8 encoding=SIGNED >> >> Signed-off-by: Yonghong Song >> --- > > LGTM. > > Is there a plan to also add CHAR encoding bit? Not yet... Need more thinking about use cases and backward comparability issues. > > >> dwarf_loader.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/dwarf_loader.c b/dwarf_loader.c >> index d892bc3..c2ad2a0 100644 >> --- a/dwarf_loader.c >> +++ b/dwarf_loader.c >> @@ -560,7 +560,7 @@ static struct base_type *base_type__new(Dwarf_Die *die, struct cu *cu, struct co >> bt->bit_size = attr_numeric(die, DW_AT_byte_size) * 8; >> uint64_t encoding = attr_numeric(die, DW_AT_encoding); >> bt->is_bool = encoding == DW_ATE_boolean; >> - bt->is_signed = encoding == DW_ATE_signed; >> + bt->is_signed = (encoding == DW_ATE_signed) || (encoding == DW_ATE_signed_char); >> bt->is_varargs = false; >> bt->name_has_encoding = true; >> bt->float_type = encoding_to_float_type(encoding); >> -- >> 2.30.2 >>