Hi! As the following testcase shows, libffi didn't handle properly classify_arguments of structures at byte offsets not divisible by UNITS_PER_WORD. The following patch adjusts it to match what config/i386/ classify_argument does for that and also ports the PR38781 fix there (the second chunk).
This has been committed to upstream libffi already: https://github.com/libffi/libffi/commit/5651bea284ad0822eafe768e3443c2f4d7da2c8f Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk? 2021-06-16 Jakub Jelinek <ja...@redhat.com> * src/x86/ffi64.c (classify_argument): For FFI_TYPE_STRUCT set words to number of words needed for type->size + byte_offset bytes rather than just type->size bytes. Compute pos before the loop and check total size of the structure. * testsuite/libffi.call/nested_struct12.c: New test. --- libffi/src/x86/ffi64.c.jj 2020-01-14 20:02:48.557583260 +0100 +++ libffi/src/x86/ffi64.c 2021-06-15 19:50:06.059108230 +0200 @@ -217,7 +217,8 @@ classify_argument (ffi_type *type, enum case FFI_TYPE_STRUCT: { const size_t UNITS_PER_WORD = 8; - size_t words = (type->size + UNITS_PER_WORD - 1) / UNITS_PER_WORD; + size_t words = (type->size + byte_offset + UNITS_PER_WORD - 1) + / UNITS_PER_WORD; ffi_type **ptr; int i; enum x86_64_reg_class subclasses[MAX_CLASSES]; @@ -241,16 +242,16 @@ classify_argument (ffi_type *type, enum /* Merge the fields of structure. */ for (ptr = type->elements; *ptr != NULL; ptr++) { - size_t num; + size_t num, pos; byte_offset = ALIGN (byte_offset, (*ptr)->alignment); num = classify_argument (*ptr, subclasses, byte_offset % 8); if (num == 0) return 0; - for (i = 0; i < num; i++) + pos = byte_offset / 8; + for (i = 0; i < num && (i + pos) < words; i++) { - size_t pos = byte_offset / 8; classes[i + pos] = merge_classes (subclasses[i], classes[i + pos]); } --- libffi/testsuite/libffi.call/nested_struct12.c.jj 2021-06-15 20:31:43.327144303 +0200 +++ libffi/testsuite/libffi.call/nested_struct12.c 2021-06-15 20:47:13.129489263 +0200 @@ -0,0 +1,107 @@ +/* Area: ffi_call, closure_call + Purpose: Check structure passing. + Limitations: none. + PR: none. + Originator: <jinch...@ca.ibm.com> and <ja...@redhat.com> 20210609 */ + +/* { dg-do run } */ +#include "ffitest.h" + +typedef struct A { + float a, b; +} A; + +typedef struct B { + float x; + struct A y; +} B; + +B B_fn(float b0, struct B b1) +{ + struct B result; + + result.x = b0 + b1.x; + result.y.a = b0 + b1.y.a; + result.y.b = b0 + b1.y.b; + + printf("%g %g %g %g: %g %g %g\n", b0, b1.x, b1.y.a, b1.y.b, + result.x, result.y.a, result.y.b); + + return result; +} + +static void +B_gn(ffi_cif* cif __UNUSED__, void* resp, void** args, + void* userdata __UNUSED__) +{ + float b0; + struct B b1; + + b0 = *(float*)(args[0]); + b1 = *(struct B*)(args[1]); + + *(B*)resp = B_fn(b0, b1); +} + +int main (void) +{ + ffi_cif cif; + void *code; + ffi_closure *pcl = ffi_closure_alloc(sizeof(ffi_closure), &code); + void* args_dbl[3]; + ffi_type* cls_struct_fields[3]; + ffi_type* cls_struct_fields1[3]; + ffi_type cls_struct_type, cls_struct_type1; + ffi_type* dbl_arg_types[3]; + + float e_dbl = 12.125f; + struct B f_dbl = { 24.75f, { 31.625f, 32.25f } }; + + struct B res_dbl; + + cls_struct_type.size = 0; + cls_struct_type.alignment = 0; + cls_struct_type.type = FFI_TYPE_STRUCT; + cls_struct_type.elements = cls_struct_fields; + + cls_struct_type1.size = 0; + cls_struct_type1.alignment = 0; + cls_struct_type1.type = FFI_TYPE_STRUCT; + cls_struct_type1.elements = cls_struct_fields1; + + cls_struct_fields[0] = &ffi_type_float; + cls_struct_fields[1] = &ffi_type_float; + cls_struct_fields[2] = NULL; + + cls_struct_fields1[0] = &ffi_type_float; + cls_struct_fields1[1] = &cls_struct_type; + cls_struct_fields1[2] = NULL; + + + dbl_arg_types[0] = &ffi_type_float; + dbl_arg_types[1] = &cls_struct_type1; + dbl_arg_types[2] = NULL; + + CHECK(ffi_prep_cif(&cif, FFI_DEFAULT_ABI, 2, &cls_struct_type1, + dbl_arg_types) == FFI_OK); + + args_dbl[0] = &e_dbl; + args_dbl[1] = &f_dbl; + args_dbl[2] = NULL; + + ffi_call(&cif, FFI_FN(B_fn), &res_dbl, args_dbl); + /* { dg-output "12.125 24.75 31.625 32.25: 36.875 43.75 44.375" } */ + CHECK( res_dbl.x == (e_dbl + f_dbl.x)); + CHECK( res_dbl.y.a == (e_dbl + f_dbl.y.a)); + CHECK( res_dbl.y.b == (e_dbl + f_dbl.y.b)); + + CHECK(ffi_prep_closure_loc(pcl, &cif, B_gn, NULL, code) == FFI_OK); + + res_dbl = ((B(*)(float, B))(code))(e_dbl, f_dbl); + /* { dg-output "\n12.125 24.75 31.625 32.25: 36.875 43.75 44.375" } */ + CHECK( res_dbl.x == (e_dbl + f_dbl.x)); + CHECK( res_dbl.y.a == (e_dbl + f_dbl.y.a)); + CHECK( res_dbl.y.b == (e_dbl + f_dbl.y.b)); + + exit(0); +} Jakub