CI: add basic FFI struct validation

.github/workflows/main.yml

@@ -35,7 +35,34 @@ jobs:
       - name: Install Rust
         uses: dtolnay/rust-toolchain@stable
       - name: Build
-        run: cargo build ${{ matrix.extra_args }}
+        run: cargo build --all --examples ${{ matrix.extra_args }}
+      - name: Validate FFI structs
+        if: runner.os == 'Linux'
+        run: |
+          set -eu
+
+          apt-get install -y gdb
+
+          executable=target/debug/examples/pattern
+          if [[ ! -f "${executable}" ]]; then
+            echo "Test executable '${executable}' not built: skipping test"
+            exit 0
+          fi
+
+          gdb -q "${executable}" -batch \
+            -ex 'source validate-structs.py' \
+            1>script-out.txt 2>gdb-stderr.txt
+
+          if [[ $(cat ./script-out.txt) != *"ALL STRUCTS OK"* ]]; then
+            echo >&2 "ERROR: struct validation failed!"
+            echo >&2 "================================"
+            cat  >&2 ./gdb-stderr.txt
+            echo >&2 "================================"
+            cat  >&2 ./script-out.txt
+            exit 1
+          fi
+
+          echo PASSED.
       - name: Test
         run: cargo test ${{ matrix.extra_args }}
 

validate-structs.py

@@ -0,0 +1,29 @@
+# NOTE: this isn't a standalone script -- meant to be run within gdb!
+
+# gdb's rust mode doesn't parse the `<` and `>` in the types correctly
+gdb.execute('set language c++')
+
+
+checked_types = [
+    ('zydis::decoder::Decoder', 'ZydisDecoder'),
+    ('zydis::ffi::decoder::DecodedOperand', 'ZydisDecodedOperand'),
+    ('zydis::ffi::decoder::AccessedFlags<zydis::enums::CpuFlag>', 'ZydisAccessedFlags'),
+    ('zydis::ffi::decoder::AccessedFlags<zydis::enums::FpuFlag>', 'ZydisAccessedFlags'),
+    ('zydis::ffi::decoder::AvxInfo', 'ZydisDecodedInstructionAvx'),
+    ('zydis::ffi::decoder::MetaInfo', 'ZydisDecodedInstructionMeta'),
+    ('zydis::ffi::decoder::RawInfo', 'ZydisDecodedInstructionRaw'),
+]
+
+
+def sizeof(ty: str) -> int:
+    return gdb.parse_and_eval(f'sizeof({ty})')
+
+
+for bind_ty, c_ty in checked_types:
+    bind_ty_sz = sizeof(bind_ty)
+    c_ty_sz = sizeof(c_ty)
+
+    assert bind_ty_sz == c_ty_sz, \
+        f'binding type {bind_ty} is {bind_ty_sz} bytes, but expected {c_ty_sz}'
+
+print("ALL STRUCTS OK")