lib: add freestanding support

Allow building libdeflate without linking to any libc functions by using
'make FREESTANDING=1'.  When using such a library build, the user will
need to call libdeflate_set_memory_allocator() before anything else,
since malloc() and free() will be unavailable.

[Folded in fix from Ingvar Stepanyan to use -nostdlib, and made
 freestanding_tests() check that no libs are linked to.]

Update #62

.travis.yml

@@ -13,7 +13,7 @@ matrix:
         - sudo apt-get install -y libz-dev gcc-multilib libz-dev:i386
           libc6-dev-i386 valgrind clang gcc-4.8-multilib gcc-mingw-w64-i686
       script:
-        - tools/run_tests.sh native
+        - tools/run_tests.sh native freestanding
 
     - name: Checksum, static analysis, and edge case tests (Linux)
       os: linux

Makefile

@@ -26,6 +26,10 @@
 # Define DESTDIR to override the installation destination directory
 # (default: empty string)
 #
+# Define FREESTANDING to build a freestanding library, i.e. a library that
+# doesn't link to any libc functions like malloc(), free(), and memcpy().
+# All users will need to call libdeflate_set_memory_allocator().
+#
 # You can also specify custom CFLAGS, CPPFLAGS, and/or LDFLAGS.
 #
 ##############################################################################
@@ -50,7 +54,11 @@ override CFLAGS :=							\
 	$(call cc-option,-Wvla)						\
 	$(call cc-option,-Wimplicit-fallthrough)
 
-# We don't define any CPPFLAGS, but support the user specifying it.
+FREESTANDING :=
+ifdef FREESTANDING
+override CPPFLAGS += -DFREESTANDING
+LIB_CFLAGS += -ffreestanding -nostdlib
+endif
 
 ##############################################################################
 

lib/arm/cpu_features.h

@@ -8,7 +8,9 @@
 #include "../lib_common.h"
 
 #if (defined(__arm__) || defined(__aarch64__)) && \
-	defined(__linux__) && COMPILER_SUPPORTS_TARGET_FUNCTION_ATTRIBUTE
+	defined(__linux__) && \
+	COMPILER_SUPPORTS_TARGET_FUNCTION_ATTRIBUTE && \
+	!defined(FREESTANDING)
 #  define ARM_CPU_FEATURES_ENABLED 1
 #else
 #  define ARM_CPU_FEATURES_ENABLED 0

lib/deflate_compress.c

@@ -27,8 +27,6 @@
  * OTHER DEALINGS IN THE SOFTWARE.
  */
 
-#include <string.h>
-
 #include "deflate_compress.h"
 #include "deflate_constants.h"
 #include "unaligned.h"

lib/deflate_decompress.c

@@ -45,7 +45,6 @@
  */
 
 #include <limits.h>
-#include <string.h>
 
 #include "deflate_constants.h"
 #include "unaligned.h"

lib/lib_common.h

@@ -36,4 +36,13 @@ void libdeflate_free(void *ptr);
 void *libdeflate_aligned_malloc(size_t alignment, size_t size);
 void libdeflate_aligned_free(void *ptr);
 
+#ifdef FREESTANDING
+void *memset(void *s, int c, size_t n);
+void *memcpy(void *dest, const void *src, size_t n);
+void *memmove(void *dest, const void *src, size_t n);
+int memcmp(const void *s1, const void *s2, size_t n);
+#else
+#include <string.h>
+#endif
+
 #endif /* LIB_LIB_COMMON_H */

lib/utils.c

@@ -25,7 +25,12 @@
  * OTHER DEALINGS IN THE SOFTWARE.
  */
 
-#include <stdlib.h>
+#ifdef FREESTANDING
+#  define malloc NULL
+#  define free NULL
+#else
+#  include <stdlib.h>
+#endif
 
 #include "lib_common.h"
 
@@ -72,3 +77,57 @@ libdeflate_set_memory_allocator(void *(*malloc_func)(size_t),
 	libdeflate_malloc_func = malloc_func;
 	libdeflate_free_func = free_func;
 }
+
+/*
+ * Implementations of libc functions for freestanding library builds.
+ * Not optimized yet.  Normal library builds don't use these.
+ */
+#ifdef FREESTANDING
+void *memset(void *s, int c, size_t n)
+{
+	u8 *p = s;
+	size_t i;
+
+	for (i = 0; i < n; i++)
+		p[i] = c;
+	return s;
+}
+
+void *memcpy(void *dest, const void *src, size_t n)
+{
+	u8 *d = dest;
+	const u8 *s = src;
+	size_t i;
+
+	for (i = 0; i < n; i++)
+		d[i] = s[i];
+	return dest;
+}
+
+void *memmove(void *dest, const void *src, size_t n)
+{
+	u8 *d = dest;
+	const u8 *s = src;
+	size_t i;
+
+	if (d <= s)
+		return memcpy(d, s, n);
+
+	for (i = n; i > 0; i--)
+		d[i - 1] = s[i - 1];
+	return dest;
+}
+
+int memcmp(const void *s1, const void *s2, size_t n)
+{
+	const u8 *p1 = s1;
+	const u8 *p2 = s2;
+	size_t i;
+
+	for (i = 0; i < n; i++) {
+		if (p1[i] != p2[i])
+			return (int)p1[i] - (int)p2[i];
+	}
+	return 0;
+}
+#endif /* FREESTANDING */

programs/prog_util.c

@@ -130,6 +130,11 @@ void
 begin_program(tchar *argv[])
 {
 	program_invocation_name = get_filename(argv[0]);
+
+#ifdef FREESTANDING
+	/* This allows testing freestanding library builds. */
+	libdeflate_set_memory_allocator(malloc, free);
+#endif
 }
 
 /* Create a copy of 'path' surrounded by double quotes */

tools/run_tests.sh

@@ -173,6 +173,33 @@ native_tests() {
 	fi
 }
 
+# Test the library built with FREESTANDING=1.
+freestanding_tests() {
+	test_group_included freestanding || return 0
+
+	WRAPPER= native_build_and_test FREESTANDING=1
+	if nm libdeflate.so | grep ' U ' > "$TMPFILE"; then
+		echo 1>&2 "Freestanding lib links to external functions!:"
+		nm libdeflate.so | grep ' U '
+		return 1
+	fi
+	ldd libdeflate.so > "$TMPFILE"
+	if grep -q -v 'statically linked' "$TMPFILE"; then
+		echo 1>&2 "Freestanding lib links to external libraries!:"
+		cat "$TMPFILE"
+		return 1
+	fi
+
+	if have_valgrind; then
+		WRAPPER="$VALGRIND" native_build_and_test FREESTANDING=1
+	fi
+
+	if have_ubsan; then
+		WRAPPER= native_build_and_test FREESTANDING=1 \
+			CC=clang CFLAGS="$SANITIZE_CFLAGS"
+	fi
+}
+
 ###############################################################################
 
 checksum_benchmarks() {
@@ -361,6 +388,7 @@ log "	SMOKEDATA=$SMOKEDATA"
 log "	NDKDIR=$NDKDIR"
 
 native_tests
+freestanding_tests
 checksum_benchmarks
 android_tests
 mips_tests