[contrib] Add freestanding translator prototype

This is the idea, some of the functionality isn't yet implemented.

contrib/freestanding_lib/test/Makefile

@@ -0,0 +1,27 @@
+# ################################################################
+# Copyright (c) 2015-2020, Facebook, Inc.
+# All rights reserved.
+#
+# This source code is licensed under both the BSD-style license (found in the
+# LICENSE file in the root directory of this source tree) and the GPLv2 (found
+# in the COPYING file in the root directory of this source tree).
+# You may select, at your option, one of the above-listed licenses.
+# ################################################################
+
+all: run-test
+
+.PHONY: libzstd
+libzstd: clean
+	../freestanding.py --source-lib ../../../lib --output-lib ./libzstd
+
+
+test: libzstd
+	$(CC) $(CFLAGS) $(CPPFLAGS) -ffreestanding $(wildcard libzstd/*/*.c) -c
+	$(CC) $(CFLAGS) $(CPPFLAGS) -ffreestanding -c test.c
+	$(CC) $(LDFLAGS) -ffreestanding -nostdlib *.o -o test
+
+run-test: test
+	./test
+
+clean:
+	rm -rf ./libzstd/ *.o test

contrib/freestanding_lib/test/test.c

@@ -0,0 +1,99 @@
+/*
+ * Copyright (c) 2016-2020, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under both the BSD-style license (found in the
+ * LICENSE file in the root directory of this source tree) and the GPLv2 (found
+ * in the COPYING file in the root directory of this source tree).
+ * You may select, at your option, one of the above-listed licenses.
+ */
+#ifndef __x86_64__
+# error This test only works on x86-64
+#endif
+
+#include "./libzstd/zstd.h"
+
+void* ZSTD_malloc(size_t size) {
+    (void)size;
+    return NULL;
+}
+void ZSTD_free(void* ptr) {
+    (void)ptr;
+}
+void* ZSTD_calloc(size_t num, size_t size) {
+    (void)num;
+    (void)size;
+    return NULL;
+}
+
+/* The standard requires these three functions be present.
+ * The compiler is free to insert calls to these functions.
+ */
+void* memmove(void* destination, const void* source, size_t num) {
+    char* const d = (char*)destination;
+    char const* const s = (char const*)source;
+    if (s < d) {
+        for (size_t i = num; i-- > 0;) {
+            d[i] = s[i];
+        }
+    } else {
+        for (size_t i = 0; i < num; ++i) {
+            d[i] = s[i];
+        }
+    }
+    return destination;
+}
+void* memcpy(void* destination, const void* source, size_t num) {
+    return memmove(destination, source, num);
+}
+void* memset(void* destination, int value, size_t num) {
+    char* const d = (char*)destination;
+    for (size_t i = 0; i < num; ++i) {
+        d[i] = value;
+    }
+    return destination;
+}
+
+void* ZSTD_memmove(void* destination, const void* source, size_t num) {
+    return memmove(destination, source, num);
+}
+void* ZSTD_memcpy(void* destination, const void* source, size_t num) {
+    return memmove(destination, source, num);
+}
+void* ZSTD_memset(void* destination, int value, size_t num) {
+    return memset(destination, value, num);
+}
+
+int main(void) {
+    char dst[100];
+    ZSTD_CCtx* const cctx = ZSTD_createCCtx();
+    ZSTD_freeCCtx(cctx);
+    if (cctx != NULL) {
+        return 1;
+    }
+    if (!ZSTD_isError(ZSTD_compress(dst, sizeof(dst), NULL, 0, 1))) {
+        return 2;
+    }
+    return 0;
+}
+
+static inline long syscall1(long syscall, long arg1) {
+    long ret;
+    __asm__ volatile
+    (
+        "syscall"
+        : "=a" (ret)
+        : "a" (syscall), "D" (arg1)
+        : "rcx", "r11", "memory"
+    );
+    return ret;
+}
+
+static inline void exit(int status) {
+    syscall1(60, status);
+}
+
+void _start(void) {
+    int const ret = main();
+    exit(ret);
+}

contrib/freestanding_lib/test/zstd_deps.h

@@ -0,0 +1,106 @@
+/*
+ * Copyright (c) 2016-2020, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under both the BSD-style license (found in the
+ * LICENSE file in the root directory of this source tree) and the GPLv2 (found
+ * in the COPYING file in the root directory of this source tree).
+ * You may select, at your option, one of the above-listed licenses.
+ */
+
+/* Need:
+ * NULL
+ * ZSTD_memcpy()
+ * ZSTD_memset()
+ * ZSTD_memmove()
+ * BYTE
+ * S16
+ * U16
+ * U32
+ * U64
+ * size_t
+ * ptrdiff_t
+ * INT_MAX
+ * ...
+ */
+#ifndef ZSTD_DEPS_COMMON
+#define ZSTD_DEPS_COMMON
+
+#include <stddef.h>
+
+typedef unsigned char      BYTE;
+typedef unsigned short      U16;
+typedef   signed short      S16;
+typedef unsigned int        U32;
+typedef   signed int        S32;
+typedef unsigned long long  U64;
+typedef   signed long long  S64;
+
+#ifndef INT_MAX
+# define INT_MAX ((int)((1u << 31) - 1))
+#endif
+
+#if defined(__GNUC__) && __GNUC__ >= 4
+#define ZSTD_memcpy(d,s,n) __builtin_memcpy((d),(s),(n))
+#define ZSTD_memmove(d,s,n) __builtin_memmove((d),(s),(n))
+#define ZSTD_memset(d,s,n) __builtin_memset((d),(s),(n))
+#else
+void* ZSTD_memcpy(void* destination, const void* source, size_t num);
+void* ZSTD_memmove(void* destination, const void* source, size_t num);
+void* ZSTD_memset(void* destination, int value, size_t num);
+#endif
+
+#endif /* ZSTD_DEPS_COMMON */
+
+/* Need:
+ * ZSTD_malloc()
+ * ZSTD_free()
+ * ZSTD_calloc()
+ */
+#ifdef ZSTD_DEPS_NEED_MALLOC
+#ifndef ZSTD_DEPS_MALLOC
+#define ZSTD_DEPS_MALLOC
+
+void* ZSTD_malloc(size_t size);
+void ZSTD_free(void* ptr);
+void* ZSTD_calloc(size_t num, size_t size);
+
+#endif /* ZSTD_DEPS_MALLOC */
+#endif /* ZSTD_DEPS_NEED_MALLOC */
+
+/* Need:
+ * assert()
+ */
+#ifdef ZSTD_DEPS_NEED_ASSERT
+#ifndef ZSTD_DEPS_ASSERT
+#define ZSTD_DEPS_ASSERT
+
+#define assert(x) ((void)0)
+
+#endif /* ZSTD_DEPS_ASSERT */
+#endif /* ZSTD_DEPS_NEED_ASSERT */
+
+/* Need:
+ * ZSTD_DEBUG_PRINT()
+ */
+#ifdef ZSTD_DEPS_NEED_IO
+#ifndef ZSTD_DEPS_IO
+#define ZSTD_DEPS_IO
+
+#define ZSTD_DEBUG_PRINT(...) 
+
+#endif /* ZSTD_DEPS_IO */
+#endif /* ZSTD_DEPS_NEED_IO */
+
+/* Only requested when <stdint.h> is known to be present.
+ * Need:
+ * intptr_t
+ */
+#ifdef ZSTD_DEPS_NEED_STDINT
+#ifndef ZSTD_DEPS_STDINT
+#define ZSTD_DEPS_STDINT
+
+#define intptr_t size_t
+
+#endif /* ZSTD_DEPS_STDINT */
+#endif /* ZSTD_DEPS_NEED_STDINT */