Add ABI checking tool for release process

doc/release-process.md

@@ -34,6 +34,11 @@ build=$(mktemp -d)
 cmake -B $build -DCMAKE_INSTALL_PREFIX=$dir && cmake --build $build --target install && ls -RlAh $dir
 gcc -o ecdsa examples/ecdsa.c -I $dir/include -L $dir/lib*/ -l secp256k1 -Wl,-rpath,"$dir/lib",-rpath,"$dir/lib64" && ./ecdsa
 ```
+4. Use the [`check-abi.sh`](/tools/check-abi.sh) tool to ensure there are no unexpected ABI incompatibilities and that the version number and release notes accurately reflect all potential ABI changes. To run this tool, the `abi-dumper` and `abi-compliance-checker` packages are required.
+
+```shell
+tools/check-abi.sh
+```
 
 ## Regular release
 

tools/check-abi.sh

@@ -0,0 +1,64 @@
+#!/bin/sh
+
+set -eu
+
+default_base_version="$(git describe --match "v*.*.*" --abbrev=0)"
+default_new_version="master"
+
+display_help_and_exit() {
+    echo "Usage: $0 <base_ver> <new_ver>"
+    echo ""
+    echo "Description: This script uses the ABI Compliance Checker tool to determine if the ABI"
+    echo "             of a new version of libsecp256k1 has changed in a backward-incompatible way."
+    echo ""
+    echo "Options:"
+    echo "  base_ver      Specify the base version (default: $default_base_version)"
+    echo "  new_ver       Specify the new version (default: $default_new_version)"
+    echo "  -h, --help    Display this help message"
+    exit 0
+}
+
+if [ "$#" -eq 0 ]; then
+    base_version="$default_base_version"
+    new_version="$default_new_version"
+elif [ "$#" -eq 1 ] && { [ "$1" = "-h" ] || [ "$1" = "--help" ]; }; then
+    display_help_and_exit
+elif [ "$#" -eq 2 ]; then
+    base_version="$1"
+    new_version="$2"
+else
+    echo "Invalid usage. See help:"
+    echo ""
+    display_help_and_exit
+fi
+
+checkout_and_build() {
+    git worktree add -d "$1" "$2"
+    cd "$1"
+    mkdir build && cd build
+    cmake -S .. --preset dev-mode \
+        -DCMAKE_C_COMPILER=gcc -DCMAKE_BUILD_TYPE=None -DCMAKE_C_FLAGS="-g -Og -gdwarf-4" \
+        -DSECP256K1_BUILD_BENCHMARK=OFF \
+        -DSECP256K1_BUILD_TESTS=OFF \
+        -DSECP256K1_BUILD_EXHAUSTIVE_TESTS=OFF \
+        -DSECP256K1_BUILD_CTIME_TESTS=OFF \
+        -DSECP256K1_BUILD_EXAMPLES=OFF
+    cmake --build . -j "$(nproc)"
+    abi-dumper src/libsecp256k1.so -o ABI.dump -lver "$2"
+}
+
+echo "Comparing $base_version (base version) to $new_version (new version)"
+echo
+
+original_dir="$(pwd)"
+
+base_source_dir=$(mktemp -d)
+checkout_and_build "$base_source_dir" "$base_version"
+
+new_source_dir=$(mktemp -d)
+checkout_and_build "$new_source_dir" "$new_version"
+
+cd "$original_dir"
+abi-compliance-checker -lib libsecp256k1 -old "${base_source_dir}/build/ABI.dump" -new "${new_source_dir}/build/ABI.dump"
+git worktree remove "$base_source_dir"
+git worktree remove "$new_source_dir"