[trace] Remove default definitions of weak symbols

Instead of providing a default no-op implementation, check the symbols
for `NULL` before accessing them. Providing a default implementation
doesn't reliably work with dynamic linking. Depending on link order the
default implementations may not be overridden. By skipping the default
implementation, all link order issues are resolved. If the symbols
aren't provided the weak function will be `NULL`.

build/meson/lib/meson.build

@@ -22,7 +22,6 @@ libzstd_sources = [join_paths(zstd_rootdir, 'lib/common/entropy_common.c'),
   join_paths(zstd_rootdir, 'lib/common/threading.c'),
   join_paths(zstd_rootdir, 'lib/common/pool.c'),
   join_paths(zstd_rootdir, 'lib/common/zstd_common.c'),
-  join_paths(zstd_rootdir, 'lib/common/zstd_trace.c'),
   join_paths(zstd_rootdir, 'lib/common/error_private.c'),
   join_paths(zstd_rootdir, 'lib/common/xxhash.c'),
   join_paths(zstd_rootdir, 'lib/compress/hist.c'),

lib/common/zstd_trace.h

@@ -114,14 +114,15 @@ typedef unsigned long long ZSTD_TraceCtx;
  * @returns Non-zero if tracing is enabled. The return value is
  *          passed to ZSTD_trace_compress_end().
  */
-ZSTD_TraceCtx ZSTD_trace_compress_begin(struct ZSTD_CCtx_s const* cctx);
+ZSTD_WEAK_ATTR ZSTD_TraceCtx ZSTD_trace_compress_begin(
+    struct ZSTD_CCtx_s const* cctx);
 
 /**
  * Trace the end of a compression call.
  * @param ctx The return value of ZSTD_trace_compress_begin().
  * @param trace The zstd tracing info.
  */
-void ZSTD_trace_compress_end(
+ZSTD_WEAK_ATTR void ZSTD_trace_compress_end(
     ZSTD_TraceCtx ctx,
     ZSTD_Trace const* trace);
 
@@ -132,14 +133,15 @@ void ZSTD_trace_compress_end(
  * @returns Non-zero if tracing is enabled. The return value is
  *          passed to ZSTD_trace_compress_end().
  */
-ZSTD_TraceCtx ZSTD_trace_decompress_begin(struct ZSTD_DCtx_s const* dctx);
+ZSTD_WEAK_ATTR ZSTD_TraceCtx ZSTD_trace_decompress_begin(
+    struct ZSTD_DCtx_s const* dctx);
 
 /**
  * Trace the end of a decompression call.
  * @param ctx The return value of ZSTD_trace_decompress_begin().
  * @param trace The zstd tracing info.
  */
-void ZSTD_trace_decompress_end(
+ZSTD_WEAK_ATTR void ZSTD_trace_decompress_end(
     ZSTD_TraceCtx ctx,
     ZSTD_Trace const* trace);
 

lib/compress/zstd_compress.c

@@ -4379,7 +4379,7 @@ static size_t ZSTD_compressBegin_internal(ZSTD_CCtx* cctx,
                                     ZSTD_buffered_policy_e zbuff)
 {
 #if ZSTD_TRACE
-    cctx->traceCtx = ZSTD_trace_compress_begin(cctx);
+    cctx->traceCtx = (ZSTD_trace_compress_begin != NULL) ? ZSTD_trace_compress_begin(cctx) : 0;
 #endif
     DEBUGLOG(4, "ZSTD_compressBegin_internal: wlog=%u", params->cParams.windowLog);
     /* params are supposed to be fully validated at this point */
@@ -4510,7 +4510,7 @@ static size_t ZSTD_writeEpilogue(ZSTD_CCtx* cctx, void* dst, size_t dstCapacity)
 void ZSTD_CCtx_trace(ZSTD_CCtx* cctx, size_t extraCSize)
 {
 #if ZSTD_TRACE
-    if (cctx->traceCtx) {
+    if (cctx->traceCtx && ZSTD_trace_compress_end != NULL) {
         int const streaming = cctx->inBuffSize > 0 || cctx->outBuffSize > 0 || cctx->appliedParams.nbWorkers > 0;
         ZSTD_Trace trace;
         ZSTD_memset(&trace, 0, sizeof(trace));
@@ -5456,7 +5456,7 @@ static size_t ZSTD_CCtx_init_compressStream2(ZSTD_CCtx* cctx,
     }
     if (params.nbWorkers > 0) {
 #if ZSTD_TRACE
-        cctx->traceCtx = ZSTD_trace_compress_begin(cctx);
+        cctx->traceCtx = (ZSTD_trace_compress_begin != NULL) ? ZSTD_trace_compress_begin(cctx) : 0;
 #endif
         /* mt context creation */
         if (cctx->mtctx == NULL) {

lib/decompress/zstd_decompress.c

@@ -788,7 +788,7 @@ static size_t ZSTD_setRleBlock(void* dst, size_t dstCapacity,
 static void ZSTD_DCtx_trace_end(ZSTD_DCtx const* dctx, U64 uncompressedSize, U64 compressedSize, unsigned streaming)
 {
 #if ZSTD_TRACE
-    if (dctx->traceCtx) {
+    if (dctx->traceCtx && ZSTD_trace_decompress_end != NULL) {
         ZSTD_Trace trace;
         ZSTD_memset(&trace, 0, sizeof(trace));
         trace.version = ZSTD_VERSION_NUMBER;
@@ -1383,7 +1383,7 @@ size_t ZSTD_decompressBegin(ZSTD_DCtx* dctx)
 {
     assert(dctx != NULL);
 #if ZSTD_TRACE
-    dctx->traceCtx = ZSTD_trace_decompress_begin(dctx);
+    dctx->traceCtx = (ZSTD_trace_decompress_begin != NULL) ? ZSTD_trace_decompress_begin(dctx) : 0;
 #endif
     dctx->expected = ZSTD_startingInputLength(dctx->format);  /* dctx->format must be properly set */
     dctx->stage = ZSTDds_getFrameHeaderSize;