Fuzzing: compile the whole libespeak with -fsanitize=fuzzer-no-link

-fsanitize=fuzzer-no-link makes it workable to build a library with fuzzing
enabled, and let the fuzzing test program explicitly trigger the fuzzing.

This allows fuzzing to trace cmp instructions to guide the fuzzing to
improve results.

.github/workflows/fuzzing.yml

@@ -16,6 +16,7 @@ jobs:
         include:
           - arch: x86-32
             archdeps: "gcc-multilib g++-multilib libpcaudio-dev:i386 libsonic-dev:i386 libc6-dbg:i386"
+            archconfig: "--host=i686-linux-gnu"
             archconfigflags: "-m32"
 
           - arch: x86-64
@@ -31,11 +32,11 @@ jobs:
     - name: autoconf
       run: ./autogen.sh ; chmod -x INSTALL m4/*.m4
     - name: configure
-      run: CC=clang CXX=clang++
-           CFLAGS="${{ matrix.archconfigflags }} -fsanitize=address,undefined -fstack-protector-strong -g -Og -fno-omit-frame-pointer"
+      run: CC="clang ${{ matrix.archconfigflags }}" CXX="clang++ ${{ matrix.archconfigflags }}"
+           CFLAGS="-fsanitize=address,undefined -fstack-protector-strong -g -Og -fno-omit-frame-pointer"
            CXXFLAGS="${{ matrix.archconfigflags }} -fsanitize=address,undefined -fstack-protector-strong -g -Og -fno-omit-frame-pointer"
            LDFLAGS="-fsanitize=address,undefined -lubsan"
-           ./configure --with-libfuzzer
+           ./configure ${{ matrix.archconfig }} --with-libfuzzer
     - name: Store the fuzzer config
       if: ${{ failure() }}
       uses: actions/upload-artifact@v3

Makefile.am

@@ -262,7 +262,7 @@ man1_MANS += src/speak-ng.1
 endif
 
 src_speak_ng_LDADD   = src/libespeak-ng.la
-src_speak_ng_LDFLAGS = -static -lm ${PCAUDIOLIB_LIBS}
+src_speak_ng_LDFLAGS = -static -lm ${PCAUDIOLIB_LIBS} ${LIBFUZZER_NO_MAIN}
 src_speak_ng_CFLAGS  = -Isrc/libespeak-ng ${AM_CFLAGS}
 
 bin_PROGRAMS += src/espeak-ng
@@ -271,7 +271,7 @@ if HAVE_RONN
 man1_MANS += src/espeak-ng.1
 endif
 
-src_espeak_ng_LDADD   = src/libespeak-ng.la ${PCAUDIOLIB_LIBS}
+src_espeak_ng_LDADD   = src/libespeak-ng.la ${PCAUDIOLIB_LIBS} ${LIBFUZZER_NO_MAIN}
 src_espeak_ng_SOURCES = src/espeak-ng.c
 if HAVE_LIBFUZZER
 nodist_EXTRA_src_espeak_ng_SOURCES = force-cxx-linking.cxx
@@ -354,14 +354,11 @@ endif
 
 
 if HAVE_LIBFUZZER
-tests_ssml_fuzzer_test_CFLAGS += -fsanitize=fuzzer
-tests_ssml_fuzzer_test_LDFLAGS = -fsanitize=fuzzer
-
 noinst_PROGRAMS =  tests/fuzzing/synth_fuzzer.test
 tests_fuzzing_synth_fuzzer_test_SOURCES = tests/fuzzing/synth_fuzzer.c
 tests_fuzzing_synth_fuzzer_test_LDADD =  src/libespeak-ng.la
-tests_fuzzing_synth_fuzzer_test_CFLAGS=  ${AM_CFLAGS} -fsanitize=fuzzer -DPATH_ESPEAK_DATA=\"$(abs_top_srcdir)/espeak-ng-data\" -Isrc/libespeak-ng
-tests_fuzzing_synth_fuzzer_test_LDFLAGS= ${AM_LDFLAGS} -fsanitize=fuzzer -static -lm -Wl,-z,relro ${PCAUDIOLIB_LIBS}
+tests_fuzzing_synth_fuzzer_test_CFLAGS=  ${AM_CFLAGS} -DPATH_ESPEAK_DATA=\"$(abs_top_srcdir)/espeak-ng-data\" -Isrc/libespeak-ng
+tests_fuzzing_synth_fuzzer_test_LDFLAGS= ${AM_LDFLAGS} -static -lm -Wl,-z,relro ${PCAUDIOLIB_LIBS} ${LIBFUZZER_NO_MAIN}
 else
 tests_ssml_fuzzer_test_LDADD += tests/libfuzzrunner.la
 endif

configure.ac

@@ -136,17 +136,28 @@ else
 fi
 
 
-AC_LANG_PUSH(C)
-TEMP_CFLAGS="$CFLAGS"
-CFLAGS="$CFLAGS -fsanitize=fuzzer"
-AC_MSG_CHECKING([if $CC supports fuzzer with the -fsanitize=fuzzer flag])
-AC_COMPILE_IFELSE(
-	[AC_LANG_PROGRAM( [[]], [[]])],
-	[have_fuzzer_fuzzer=yes],
-	[have_fuzzer_fuzzer=no])
-AC_MSG_RESULT($have_fuzzer_fuzzer)
-CFLAGS="$TEMP_CFLAGS"
-AC_LANG_POP(C)
+if test "$with_libfuzzer" = yes ; then
+	AC_LANG_PUSH(C)
+	TEMP_CFLAGS="$CFLAGS"
+	TEMP_LIBS="$LIBS"
+	HOST_CPU="`$CC -print-multiarch | sed -e 's/-.*//'`"
+	LIBFUZZER_NO_MAIN="`$CC -print-runtime-dir`/libclang_rt.fuzzer_no_main-$HOST_CPU.a -lstdc++ -lm"
+	CFLAGS="$CFLAGS -fsanitize=fuzzer-no-link"
+	LIBS="$LIBS $LIBFUZZER_NO_MAIN"
+	AC_MSG_CHECKING([if $CC supports fuzzer with the -fsanitize=fuzzer flag])
+	AC_COMPILE_IFELSE(
+		[AC_LANG_PROGRAM( [[]], [[]])],
+		[have_fuzzer_fuzzer=yes],
+		[have_fuzzer_fuzzer=no])
+	AC_MSG_RESULT($have_fuzzer_fuzzer)
+	if test "$have_fuzzer_fuzzer" != yes ; then
+		CFLAGS="$TEMP_CFLAGS"
+		LIBFUZZER_NO_MAIN=""
+	fi
+	AC_SUBST(LIBFUZZER_NO_MAIN)
+	LIBS="$TEMP_LIBS"
+	AC_LANG_POP(C)
+fi
 
 dnl ================================================================
 dnl FreeBSD check.

tests/fuzzing/synth_fuzzer.c

@@ -40,10 +40,10 @@ espeak_callback(short *data, int samples, espeak_EVENT *events)
 }
 
 /* See http://llvm.org/docs/LibFuzzer.html */
-extern int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size);
-
-extern int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size)
+extern int LLVMFuzzerRunDriver(int *argc, char ***argv,
+                  int (*UserCb)(const uint8_t *Data, size_t Size));
 
+int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size)
 {
 	int buflength = size+1;
 	if (!initialized)
@@ -78,3 +78,7 @@ extern int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size)
 
 	return 0;
 }
+
+int main(int argc, char *argv[]) {
+	LLVMFuzzerRunDriver(&argc, &argv, LLVMFuzzerTestOneInput);
+}