Sorry for a delay.
Here are C function (from reconstructed bug example):
double c_fn( double a, double b) {
return a * b;
}
and uffi definition:
(def-function ("c_fn" c_fn) ((a :double) (b :double)) :returning :double)
The resulting asm code for C function:
<c_fn>:
0: 55 push %ebp
1: 89 e5 mov %esp,%ebp
3: dd 45 10 fldl 0x10(%ebp)
6: dc 4d 08 fmull 0x8(%ebp)
9: 5d pop %ebp
a: c3 ret
and UFFI wrapper:
<L1c_fn>:
a60: 56 push %esi
a61: 53 push %ebx
a62: e8 f4 fe ff ff call 95b <__x86.get_pc_thunk.bx>
a67: 81 c3 2d 07 00 00 add $0x72d,%ebx
a6d: 83 ec 34 sub $0x34,%esp
a70: e8 4b fd ff ff call 7c0 <ecl_process_env@plt>
a75: 89 c6 mov %eax,%esi
a77: 8d 44 24 2c lea 0x2c(%esp),%eax
a7b: 39 86 58 01 00 00 cmp %eax,0x158(%esi)
a81: 73 49 jae acc <L1c_fn+0x6c>
a83: 8b 44 24 44 mov 0x44(%esp),%eax
a87: 89 04 24 mov %eax,(%esp)
a8a: e8 a1 fd ff ff call 830 <ecl_to_double@plt>
a8f: 8b 44 24 40 mov 0x40(%esp),%eax
a93: 89 04 24 mov %eax,(%esp)
a96: dd 5c 24 10 fstpl 0x10(%esp)
a9a: e8 91 fd ff ff call 830 <ecl_to_double@plt>
a9f: dd 44 24 10 fldl 0x10(%esp)
aa3: dd 5c 24 08 fstpl 0x8(%esp)
aa7: dd 1c 24 fstpl (%esp)
aaa: e8 21 fd ff ff call 7d0 <c_fn@plt>
aaf: 89 44 24 1c mov %eax,0x1c(%esp)
ab3: db 44 24 1c fildl 0x1c(%esp)
ab7: dd 1c 24 fstpl (%esp)
aba: e8 21 fd ff ff call 7e0 <ecl_make_double_float@plt>
abf: c7 46 04 01 00 00 00 movl $0x1,0x4(%esi)
ac6: 83 c4 34 add $0x34,%esp
ac9: 5b pop %ebx
aca: 5e pop %esi
acb: c3 ret
acc: e8 1f fd ff ff call 7f0 <ecl_cs_overflow@plt>
ad1: eb b0 jmp a83 <L1c_fn+0x23>
ad3: 8d b6 00 00 00 00 lea 0x0(%esi),%esi
ad9: 8d bc 27 00 00 00 00 lea 0x0(%edi,%eiz,1),%edi
I've also tried the same C function, but with casting result to an integer
and returning int signature, and it works fine. Compiling C code with
-mno-fp-ret-in-387 doesn't work ether.
With a C function, which calls c_ref:
double ref( double a, double b) {
return 2 * c_fn( a, b);
}
the asm listing is:
<ref>:
33: 55 push %ebp
34: 89 e5 mov %esp,%ebp
36: dd 45 10 fldl 0x10(%ebp)
39: dc 4d 08 fmull 0x8(%ebp)
3c: 5d pop %ebp
3d: d9 e8 fld1
3f: de c1 faddp %st,%st(1)
41: c3 ret
So, i believe that an uffi wrapper should use ST register, instead of
fildl and fstpl sequence.
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