Add API compatibility check tool

test/Makefile

@@ -42,6 +42,9 @@ test : test.cc include_httplib.cc ../httplib.h Makefile cert.pem
 test_split : test.cc ../httplib.h httplib.cc Makefile cert.pem
 	$(CXX) -o $@ $(CXXFLAGS) test.cc httplib.cc $(TEST_ARGS)
 
+check_abi:
+	@./check-shared-library-abi-compatibility.sh
+
 test_proxy : test_proxy.cc ../httplib.h Makefile cert.pem
 	$(CXX) -o $@ -I.. $(CXXFLAGS) test_proxy.cc $(TEST_ARGS)
 

test/check-abi-compatibility.sh

@@ -0,0 +1,59 @@
+#!/bin/bash
+if [ "$#" -ne 2 ]; then
+    echo "Usage: $0 old_library.so new_library.so"
+    exit 1
+fi
+
+OLD_LIB=$1
+NEW_LIB=$2
+
+OLD_FUNCS=_old_funcs.txt
+NEW_FUNCS=_new_funcs.txt
+OLD_VARS=_old_vars.txt
+NEW_VARS=_new_vars.txt
+
+# Extract function symbols from the old and new libraries
+nm -C --defined-only $OLD_LIB | c++filt | awk '$2 ~ /[TW]/ {print substr($0, index($0,$3))}' | sort > $OLD_FUNCS
+nm -C --defined-only $NEW_LIB | c++filt | awk '$2 ~ /[TW]/ {print substr($0, index($0,$3))}' | sort > $NEW_FUNCS
+
+# Extract variable symbols from the old and new libraries
+nm -C --defined-only $OLD_LIB | c++filt | awk '$2 ~ /[BDG]/ {print substr($0, index($0,$3))}' | sort > $OLD_VARS
+nm -C --defined-only $NEW_LIB | c++filt | awk '$2 ~ /[BDG]/ {print substr($0, index($0,$3))}' | sort > $NEW_VARS
+
+# Initialize error flag and message
+error_flag=0
+error_message=""
+
+# Check for removed function symbols
+removed_funcs=$(comm -23 $OLD_FUNCS $NEW_FUNCS)
+if [ -n "$removed_funcs" ]; then
+    error_flag=1
+    error_message+="[Removed Functions]\n$removed_funcs\n"
+fi
+
+# Check for removed variable symbols
+removed_vars=$(comm -23 $OLD_VARS $NEW_VARS)
+if [ -n "$removed_vars" ]; then
+    error_flag=1
+    error_message+="[Removed Variables]\n$removed_vars\n"
+fi
+
+# Check for added variable symbols
+added_vars=$(comm -13 $OLD_VARS $NEW_VARS)
+if [ -n "$added_vars" ]; then
+    error_flag=1
+    error_message+="[Added Variables]\n$added_vars\n"
+fi
+
+# Remove temporary files
+rm -f $NEW_FUNCS $OLD_FUNCS $OLD_VARS $NEW_VARS
+
+# Display error messages if any
+if [ "$error_flag" -eq 1 ]; then
+    echo -e "$error_message"
+    echo "ABI compatibility check failed."
+    exit 1
+fi
+
+echo "ABI compatibility check passed: No variable symbols were removed or added, and no function symbols were removed."
+exit 0

test/check-shared-library-abi-compatibility.sh

@@ -0,0 +1,58 @@
+#!/usr/bin/env bash
+CURRENT_COMMIT=$(git rev-parse HEAD)
+PREVIOUS_VERSION=$(git describe --tags --abbrev=0 $CURRENT_COMMIT)
+
+BUILD_DIR=_build_for_is_abi_compatible
+
+# Make the build directory
+rm -rf $BUILD_DIR
+mkdir -p $BUILD_DIR/new
+mkdir -p $BUILD_DIR/old
+
+cd $BUILD_DIR
+
+# Build the current commit
+cd new
+
+cmake \
+  -DCMAKE_BUILD_TYPE=Debug \
+  -DCMAKE_CXX_FLAGS="-g -Og" \
+  -DBUILD_SHARED_LIBS=ON \
+  -DHTTPLIB_COMPILE=ON \
+  -DCMAKE_INSTALL_PREFIX=./out \
+  ../../.. > /dev/null
+
+cmake --build . --target install > /dev/null
+cmake --build . --target clean > /dev/null
+
+cd ..
+
+# Build the nearest vesion
+cd old
+cmake \
+  -DCMAKE_BUILD_TYPE=Debug \
+  -DCMAKE_CXX_FLAGS="-g -Og" \
+  -DBUILD_SHARED_LIBS=ON \
+  -DHTTPLIB_COMPILE=ON \
+  -DCMAKE_INSTALL_PREFIX=./out \
+  ../../.. > /dev/null
+
+git checkout -q "${PREVIOUS_VERSION}"
+cmake --build . --target install > /dev/null
+cmake --build . --target clean > /dev/null
+
+cd ..
+
+# Checkout the original commit
+if [ "$CURRENT_COMMIT" = "$(git rev-parse master)" ]; then
+  git checkout -q  master
+else
+  git checkout -q "${CURRENT_COMMIT}"
+fi
+
+# ABI compatibility check
+../check-abi-compatibility.sh ./old/out/lib/libcpp-httplib.so ./new/out/lib/libcpp-httplib.so
+
+# Clean the build directory
+cd ..
+rm -rf $BUILD_DIR