Stop suppressing pointer-overflow UBSAN errors

* Remove all pointer-overflow suppressions from our UBSAN builds/tests.
* Add `ZSTD_ALLOW_POINTER_OVERFLOW_ATTR` macro to suppress
  pointer-overflow at a per-function level. This is a superior approach
  because it also applies to users who build zstd with UBSAN.
* Add `ZSTD_wrappedPtr{Diff,Add,Sub}()` that use these suppressions.
  The end goal is to only tag these functions with
  `ZSTD_ALLOW_POINTER_OVERFLOW`. But we can start by annoting functions
  that rely on pointer overflow, and gradually transition to using
  these.
* Add `ZSTD_maybeNullPtrAdd()` to simplify pointer addition when the
  pointer may be `NULL`.
* Fix all the fuzzer issues that came up. I'm sure there will be a lot
  more, but these are the ones that came up within a few minutes of
  running the fuzzers, and while running GitHub CI.

lib/legacy/zstd_legacy.h

@@ -124,6 +124,20 @@ MEM_STATIC size_t ZSTD_decompressLegacy(
                const void* dict,size_t dictSize)
 {
     U32 const version = ZSTD_isLegacy(src, compressedSize);
+    char x;
+    /* Avoid passing NULL to legacy decoding. */
+    if (dst == NULL) {
+        assert(dstCapacity == 0);
+        dst = &x;
+    }
+    if (src == NULL) {
+        assert(compressedSize == 0);
+        src = &x;
+    }
+    if (dict == NULL) {
+        assert(dictSize == 0);
+        dict = &x;
+    }
     (void)dst; (void)dstCapacity; (void)dict; (void)dictSize;  /* unused when ZSTD_LEGACY_SUPPORT >= 8 */
     switch(version)
     {
@@ -287,6 +301,12 @@ MEM_STATIC size_t ZSTD_freeLegacyStreamContext(void* legacyContext, U32 version)
 MEM_STATIC size_t ZSTD_initLegacyStream(void** legacyContext, U32 prevVersion, U32 newVersion,
                                         const void* dict, size_t dictSize)
 {
+    char x;
+    /* Avoid passing NULL to legacy decoding. */
+    if (dict == NULL) {
+        assert(dictSize == 0);
+        dict = &x;
+    }
     DEBUGLOG(5, "ZSTD_initLegacyStream for v0.%u", newVersion);
     if (prevVersion != newVersion) ZSTD_freeLegacyStreamContext(*legacyContext, prevVersion);
     switch(newVersion)
@@ -346,6 +366,16 @@ MEM_STATIC size_t ZSTD_initLegacyStream(void** legacyContext, U32 prevVersion, U
 MEM_STATIC size_t ZSTD_decompressLegacyStream(void* legacyContext, U32 version,
                                               ZSTD_outBuffer* output, ZSTD_inBuffer* input)
 {
+    static char x;
+    /* Avoid passing NULL to legacy decoding. */
+    if (output->dst == NULL) {
+        assert(output->size == 0);
+        output->dst = &x;
+    }
+    if (input->src == NULL) {
+        assert(input->size == 0);
+        input->src = &x;
+    }
     DEBUGLOG(5, "ZSTD_decompressLegacyStream for v0.%u", version);
     switch(version)
     {

lib/legacy/zstd_v01.c

@@ -14,6 +14,7 @@
 ******************************************/
 #include <stddef.h>    /* size_t, ptrdiff_t */
 #include "zstd_v01.h"
+#include "../common/compiler.h"
 #include "../common/error_private.h"
 
 
@@ -2118,6 +2119,7 @@ size_t ZSTDv01_decompressContinue(ZSTDv01_Dctx* dctx, void* dst, size_t maxDstSi
         }
         ctx->phase = 1;
         ctx->expected = ZSTD_blockHeaderSize;
+        if (ZSTDv01_isError(rSize)) return rSize;
         ctx->previousDstEnd = (void*)( ((char*)dst) + rSize);
         return rSize;
     }

lib/legacy/zstd_v02.c

@@ -11,6 +11,7 @@
 
 #include <stddef.h>    /* size_t, ptrdiff_t */
 #include "zstd_v02.h"
+#include "../common/compiler.h"
 #include "../common/error_private.h"
 
 
@@ -71,20 +72,6 @@ extern "C" {
 #include <string.h>    /* memcpy */
 
 
-/******************************************
-*  Compiler-specific
-******************************************/
-#if defined(__GNUC__)
-#  define MEM_STATIC static __attribute__((unused))
-#elif defined (__cplusplus) || (defined (__STDC_VERSION__) && (__STDC_VERSION__ >= 199901L) /* C99 */)
-#  define MEM_STATIC static inline
-#elif defined(_MSC_VER)
-#  define MEM_STATIC static __inline
-#else
-#  define MEM_STATIC static  /* this version may generate warnings for unused static functions; disable the relevant warning */
-#endif
-
-
 /****************************************************************
 *  Basic Types
 *****************************************************************/
@@ -3431,6 +3418,7 @@ static size_t ZSTD_decompressContinue(ZSTD_DCtx* ctx, void* dst, size_t maxDstSi
         }
         ctx->phase = 1;
         ctx->expected = ZSTD_blockHeaderSize;
+        if (ZSTD_isError(rSize)) return rSize;
         ctx->previousDstEnd = (void*)( ((char*)dst) + rSize);
         return rSize;
     }

lib/legacy/zstd_v03.c

@@ -11,6 +11,7 @@
 
 #include <stddef.h>    /* size_t, ptrdiff_t */
 #include "zstd_v03.h"
+#include "../common/compiler.h"
 #include "../common/error_private.h"
 
 
@@ -72,20 +73,6 @@ extern "C" {
 #include <string.h>    /* memcpy */
 
 
-/******************************************
-*  Compiler-specific
-******************************************/
-#if defined(__GNUC__)
-#  define MEM_STATIC static __attribute__((unused))
-#elif defined (__cplusplus) || (defined (__STDC_VERSION__) && (__STDC_VERSION__ >= 199901L) /* C99 */)
-#  define MEM_STATIC static inline
-#elif defined(_MSC_VER)
-#  define MEM_STATIC static __inline
-#else
-#  define MEM_STATIC static  /* this version may generate warnings for unused static functions; disable the relevant warning */
-#endif
-
-
 /****************************************************************
 *  Basic Types
 *****************************************************************/
@@ -3071,6 +3058,7 @@ static size_t ZSTD_decompressContinue(ZSTD_DCtx* ctx, void* dst, size_t maxDstSi
         }
         ctx->phase = 1;
         ctx->expected = ZSTD_blockHeaderSize;
+        if (ZSTD_isError(rSize)) return rSize;
         ctx->previousDstEnd = (void*)( ((char*)dst) + rSize);
         return rSize;
     }

lib/legacy/zstd_v04.c

@@ -16,6 +16,7 @@
 #include <string.h>    /* memcpy */
 
 #include "zstd_v04.h"
+#include "../common/compiler.h"
 #include "../common/error_private.h"
 
 
@@ -3209,6 +3210,7 @@ static size_t ZSTD_decompressContinue(ZSTD_DCtx* ctx, void* dst, size_t maxDstSi
             }
             ctx->stage = ZSTDds_decodeBlockHeader;
             ctx->expected = ZSTD_blockHeaderSize;
+            if (ZSTD_isError(rSize)) return rSize;
             ctx->previousDstEnd = (char*)dst + rSize;
             return rSize;
         }
@@ -3536,8 +3538,8 @@ static size_t ZBUFF_decompressContinue(ZBUFF_DCtx* zbc, void* dst, size_t* maxDs
 unsigned ZBUFFv04_isError(size_t errorCode) { return ERR_isError(errorCode); }
 const char* ZBUFFv04_getErrorName(size_t errorCode) { return ERR_getErrorName(errorCode); }
 
-size_t ZBUFFv04_recommendedDInSize()  { return BLOCKSIZE + 3; }
-size_t ZBUFFv04_recommendedDOutSize() { return BLOCKSIZE; }
+size_t ZBUFFv04_recommendedDInSize(void)  { return BLOCKSIZE + 3; }
+size_t ZBUFFv04_recommendedDOutSize(void) { return BLOCKSIZE; }
 
 
 

lib/legacy/zstd_v05.c

@@ -3600,6 +3600,7 @@ size_t ZSTDv05_decompressContinue(ZSTDv05_DCtx* dctx, void* dst, size_t maxDstSi
             }
             dctx->stage = ZSTDv05ds_decodeBlockHeader;
             dctx->expected = ZSTDv05_blockHeaderSize;
+            if (ZSTDv05_isError(rSize)) return rSize;
             dctx->previousDstEnd = (char*)dst + rSize;
             return rSize;
         }

lib/legacy/zstd_v06.c

@@ -14,6 +14,7 @@
 #include <stddef.h>    /* size_t, ptrdiff_t */
 #include <string.h>    /* memcpy */
 #include <stdlib.h>    /* malloc, free, qsort */
+#include "../common/compiler.h"
 #include "../common/error_private.h"
 
 
@@ -3736,6 +3737,7 @@ size_t ZSTDv06_decompressContinue(ZSTDv06_DCtx* dctx, void* dst, size_t dstCapac
             }
             dctx->stage = ZSTDds_decodeBlockHeader;
             dctx->expected = ZSTDv06_blockHeaderSize;
+            if (ZSTDv06_isError(rSize)) return rSize;
             dctx->previousDstEnd = (char*)dst + rSize;
             return rSize;
         }

lib/legacy/zstd_v07.c

@@ -24,6 +24,7 @@
 #define HUFv07_STATIC_LINKING_ONLY   /* HUFv07_TABLELOG_ABSOLUTEMAX */
 #define ZSTDv07_STATIC_LINKING_ONLY
 
+#include "../common/compiler.h"
 #include "../common/error_private.h"
 
 
@@ -4006,8 +4007,8 @@ size_t ZSTDv07_decompressContinue(ZSTDv07_DCtx* dctx, void* dst, size_t dstCapac
             }
             dctx->stage = ZSTDds_decodeBlockHeader;
             dctx->expected = ZSTDv07_blockHeaderSize;
-            dctx->previousDstEnd = (char*)dst + rSize;
             if (ZSTDv07_isError(rSize)) return rSize;
+            dctx->previousDstEnd = (char*)dst + rSize;
             if (dctx->fParams.checksumFlag) XXH64_update(&dctx->xxhState, dst, rSize);
             return rSize;
         }