Add a method for checking if ZSTD was compiled with flags that impact determinism

lib/common/portability_macros.h

@@ -168,4 +168,23 @@
 # define ZSTD_CET_ENDBRANCH
 #endif
 
+/**
+ * ZSTD_IS_DETERMINISTIC_BUILD must be set to 0 if any compilation macro is
+ * active that impacts the compressed output.
+ *
+ * NOTE: ZSTD_MULTITHREAD is allowed to be set or unset.
+ */
+#if defined(ZSTD_CLEVEL_DEFAULT) \
+    || defined(ZSTD_EXCLUDE_DFAST_BLOCK_COMPRESSOR) \
+    || defined(ZSTD_EXCLUDE_GREEDY_BLOCK_COMPRESSOR) \
+    || defined(ZSTD_EXCLUDE_LAZY_BLOCK_COMPRESSOR) \
+    || defined(ZSTD_EXCLUDE_LAZY2_BLOCK_COMPRESSOR) \
+    || defined(ZSTD_EXCLUDE_BTLAZY2_BLOCK_COMPRESSOR) \
+    || defined(ZSTD_EXCLUDE_BTOPT_BLOCK_COMPRESSOR) \
+    || defined(ZSTD_EXCLUDE_BTULTRA_BLOCK_COMPRESSOR)
+# define ZSTD_IS_DETERMINISTIC_BUILD 0
+#else
+# define ZSTD_IS_DETERMINISTIC_BUILD 1
+#endif
+
 #endif /* ZSTD_PORTABILITY_MACROS_H */

lib/common/zstd_common.c

@@ -46,3 +46,12 @@ ZSTD_ErrorCode ZSTD_getErrorCode(size_t code) { return ERR_getErrorCode(code); }
 /*! ZSTD_getErrorString() :
  *  provides error code string from enum */
 const char* ZSTD_getErrorString(ZSTD_ErrorCode code) { return ERR_getErrorString(code); }
+
+int ZSTD_isDeterministicBuild(void)
+{
+#if ZSTD_IS_DETERMINISTIC_BUILD
+    return 1;
+#else
+    return 0;
+#endif
+}

lib/zstd.h

@@ -3138,6 +3138,18 @@ ZSTDLIB_STATIC_API ZSTD_nextInputType_e ZSTD_nextInputType(ZSTD_DCtx* dctx);
 
 
 
+/*! ZSTD_isDeterministicBuild() :
+ * Returns 1 if the library is built using standard compilation flags,
+ * and participates in determinism guarantees with other builds of the
+ * same version.
+ * If this function returns 0, it means the library was compiled with
+ * non-standard compilation flags that change the output of the
+ * compressor.
+ * This is mainly used for Zstd's determinism test suite, which is only
+ * run when this function returns 1.
+ */
+ZSTDLIB_API int ZSTD_isDeterministicBuild(void);
+
 
 /* ========================================= */
 /**       Block level API (DEPRECATED)       */

programs/zstdcli.c

@@ -695,7 +695,10 @@ static void printVersion(void)
         #ifdef PLATFORM_POSIX_VERSION
             DISPLAYOUT("PLATFORM_POSIX_VERSION defined: %ldL\n", (long) PLATFORM_POSIX_VERSION);
         #endif
-    }   }
+
+            if (!ZSTD_isDeterministicBuild()) {
+                DISPLAYOUT("non-deterministic build\n");
+    }   }   }
 }
 
 #define ZSTD_NB_STRATEGIES 9