[OFFLOAD] Update ffi_cif structure to match libffi

[adurang]

The ffi_cif structure defined in the wrapper header is smaller than the actual structure in libffi which results in other structures being overwritten when libffi is called, and finally in a segfault.

The patch updates the structure to the correct layout as specified in ffi.h

[llvmbot]

@llvm/pr-subscribers-offload

Author: Alex (adurang)

Changes

The ffi_cif structure defined in the wrapper header is smaller than the actual structure in libffi which results in other structures being overwritten when libffi is called, and finally in a segfault.

The patch updates the structure to the correct layout as specified in ffi.h

---

Full diff: https://github.com/llvm/llvm-project/pull/128756.diff

1 Files Affected:

• (modified) offload/plugins-nextgen/host/dynamic_ffi/ffi.h (+10)

diff --git a/offload/plugins-nextgen/host/dynamic_ffi/ffi.h b/offload/plugins-nextgen/host/dynamic_ffi/ffi.h
index 80aa512236d28..33285b4aef402 100644
--- a/offload/plugins-nextgen/host/dynamic_ffi/ffi.h
+++ b/offload/plugins-nextgen/host/dynamic_ffi/ffi.h
@@ -53,6 +53,16 @@ typedef enum ffi_abi {
 #else
 #error "Unknown ABI"
 #endif
+} ffi_abi;
+
+typedef struct {
+  ffi_abi abi;
+  unsigned nargs;
+  ffi_type **arg_types;
+  ffi_type *rtype;
+  unsigned bytes;
+  unsigned flags;
+  long long extra_fields; // Longest extra field defined in the FFI sources
 } ffi_cif;
 
 #ifdef __cplusplus

[jhuber6]

Thanks for fixing this, but I really wish we could delete this and resolve #91264. The confounding issue is the fact that the OpenMP implicit arguments are eagerly prepended instead of appended late.