Re: Sv: Bad padding with bpftool btf dump .. format c

["Per Sundström XP" <per.xp.sundstrom@ericsson.com>]

> > ============ Vanilla ========== 
> > struct foo { 
> >     struct { 
> >         int  aa; 
> >         char ab; 
> >     } a; 
> >     long   :64; 
> >     int    :4; 
> >     char   b; 
> >     short  c; 
> > }; 
> > offsetof(struct foo, c)=18 
> > 
> > ============ Custom ========== 
> > struct foo { 
> >         long: 8; 
> >         long: 64; 
> >         long: 64; 
> >         char b; 
> >         short c; 
> > }; 
> 
> so I guess the issue is that the first 'long: 8' is padded to full
> long: 64 ?
> 
> looks like btf_dump_emit_bit_padding did not take into accout the gap
> on the
> begining of the struct
> 
> on the other hand you generated that header file from 'min_core_btf'
> btf data,
> which takes away all the unused fields.. it might not beeen
> considered as a
> use case before
> 
> jirka
> 

> That could be the case, but I think the 'emit_bit_padding()' will not
> really have a
> lot to do for the non sparse headers ..
>   /Per


Looks like something like this makes tings a lot better:

diff --git a/src/btf_dump.c b/src/btf_dump.c
index 12f7039..a8bd52a 100644
--- a/src/btf_dump.c
+++ b/src/btf_dump.c
@@ -881,13 +881,13 @@ static void btf_dump_emit_bit_padding(const
struct btf_dump *d,
                const char *pad_type;
                int pad_bits;
 
-               if (ptr_bits > 32 && off_diff > 32) {
+               if (align > 4 && ptr_bits > 32 && off_diff > 32) {
                        pad_type = "long";
                        pad_bits = chip_away_bits(off_diff, ptr_bits);
-               } else if (off_diff > 16) {
+               } else if (align > 2 && off_diff > 16) {
                        pad_type = "int";
                        pad_bits = chip_away_bits(off_diff, 32);
-               } else if (off_diff > 8) {
+               } else if (align > 1 && off_diff > 8) {
                        pad_type = "short";
                        pad_bits = chip_away_bits(off_diff, 16);
                } else {
  /Per