external_deps: check for bad DLL dependencies

We don't want the DLLs we build to depend on the MinGW standard library
DLLs.

Author: slipher

external_deps/build.sh

@@ -882,6 +882,30 @@ build_naclruntime() {
 	cp "scons-out/opt-linux-${NACL_ARCH}/staging/sel_ldr" "${PREFIX}/nacl_loader"
 }
 
+# Check for DLL dependencies on MinGW stuff. For MSVC platforms this is bad because it should work
+# without having MinGW installed. For MinGW platforms it is still bad because it might not work
+# when building with different flavors, or newer/older versions.
+build_depcheck() {
+	"${download_only}" && return
+
+	case "${PLATFORM}" in
+	windows-*-*)
+		local good=true
+		for dll in $(find "${PREFIX}/bin" -type f -name '*.dll'); do
+			# https://wiki.unvanquished.net/wiki/MinGW#Built-in_DLL_dependencies
+			if objdump -p "${dll}" | grep -oP '(?<=DLL Name: )(libgcc_s|libstdc|libssp|libwinpthread).*'; then
+				echo "${dll} depends on above DLLs"
+				good=false
+			fi
+		done
+		"${good}" || log ERROR 'Built DLLs depend on MinGW runtime DLLs'
+		;;
+	*)
+		log ERROR 'Unsupported platform for depcheck'
+		;;
+	esac
+}
+
 # The import libraries generated by MinGW seem to have issues, so we use LLVM's version instead.
 # So LLVM must be installed, e.g. 'sudo apt install llvm'
 build_genlib() {
@@ -1144,13 +1168,13 @@ setup_linux-arm64-default() {
 	common_setup linux aarch64-unknown-linux-gnu
 }
 
-base_windows_amd64_msvc_packages='zlib gmp nettle curl sdl2 glew png jpeg webp openal ogg vorbis opus opusfile naclsdk genlib'
+base_windows_amd64_msvc_packages='zlib gmp nettle curl sdl2 glew png jpeg webp openal ogg vorbis opus opusfile naclsdk depcheck genlib'
 all_windows_amd64_msvc_packages="${base_windows_amd64_msvc_packages}"
 
 base_windows_i686_msvc_packages="${base_windows_amd64_msvc_packages}"
 all_windows_i686_msvc_packages="${base_windows_amd64_msvc_packages}"
 
-base_windows_amd64_mingw_packages='zlib gmp nettle curl sdl2 glew png jpeg webp openal ogg vorbis opus opusfile naclsdk'
+base_windows_amd64_mingw_packages='zlib gmp nettle curl sdl2 glew png jpeg webp openal ogg vorbis opus opusfile naclsdk depcheck'
 all_windows_amd64_mingw_packages="${base_windows_amd64_mingw_packages}"
 
 base_windows_i686_mingw_packages="${base_windows_amd64_mingw_packages}"