Remove legacy support by default

CHANGELOG

@@ -1,3 +1,7 @@
+v1.6.0 (Dec 2025)
+api: legacy format support is now disabled by default
+build: `ZSTD_LEGACY_SUPPORT` defaults to `0` in Makefile and CMake
+
 V1.5.7 (Feb 2025)
 fix: compression bug in 32-bit mode associated with long-lasting sessions
 api: new method `ZSTD_compressSequencesAndLiterals()` (#4217, #4232)

build/VS2008/zstd/zstd.vcproj

@@ -45,7 +45,7 @@
 				Name="VCCLCompilerTool"
 				Optimization="0"
 				AdditionalIncludeDirectories="$(SolutionDir)..\..\lib;$(SolutionDir)..\..\lib\common;$(SolutionDir)..\..\lib\legacy;$(SolutionDir)..\..\lib\dictBuilder;$(SolutionDir)..\..\lib\compress"
-				PreprocessorDefinitions="ZSTD_MULTITHREAD=1;ZSTD_LEGACY_SUPPORT=5;WIN32;_DEBUG;_CONSOLE"
+				PreprocessorDefinitions="ZSTD_MULTITHREAD=1;ZSTD_LEGACY_SUPPORT=0;WIN32;_DEBUG;_CONSOLE"
 				MinimalRebuild="true"
 				BasicRuntimeChecks="3"
 				RuntimeLibrary="3"
@@ -122,7 +122,7 @@
 				EnableIntrinsicFunctions="true"
 				OmitFramePointers="true"
 				AdditionalIncludeDirectories="$(SolutionDir)..\..\lib;$(SolutionDir)..\..\lib\common;$(SolutionDir)..\..\lib\legacy;$(SolutionDir)..\..\lib\dictBuilder;$(SolutionDir)..\..\lib\compress"
-				PreprocessorDefinitions="ZSTD_MULTITHREAD=1;ZSTD_LEGACY_SUPPORT=5;WIN32;NDEBUG;_CONSOLE"
+				PreprocessorDefinitions="ZSTD_MULTITHREAD=1;ZSTD_LEGACY_SUPPORT=0;WIN32;NDEBUG;_CONSOLE"
 				RuntimeLibrary="0"
 				EnableFunctionLevelLinking="true"
 				UsePrecompiledHeader="0"
@@ -197,7 +197,7 @@
 				Name="VCCLCompilerTool"
 				Optimization="0"
 				AdditionalIncludeDirectories="$(SolutionDir)..\..\lib;$(SolutionDir)..\..\lib\common;$(SolutionDir)..\..\lib\legacy;$(SolutionDir)..\..\lib\dictBuilder;$(SolutionDir)..\..\lib\compress"
-				PreprocessorDefinitions="ZSTD_MULTITHREAD=1;ZSTD_LEGACY_SUPPORT=5;WIN32;_DEBUG;_CONSOLE"
+				PreprocessorDefinitions="ZSTD_MULTITHREAD=1;ZSTD_LEGACY_SUPPORT=0;WIN32;_DEBUG;_CONSOLE"
 				MinimalRebuild="true"
 				BasicRuntimeChecks="3"
 				RuntimeLibrary="3"
@@ -275,7 +275,7 @@
 				EnableIntrinsicFunctions="true"
 				OmitFramePointers="true"
 				AdditionalIncludeDirectories="$(SolutionDir)..\..\lib;$(SolutionDir)..\..\lib\common;$(SolutionDir)..\..\lib\legacy;$(SolutionDir)..\..\lib\dictBuilder;$(SolutionDir)..\..\lib\compress"
-				PreprocessorDefinitions="ZSTD_MULTITHREAD=1;ZSTD_LEGACY_SUPPORT=5;WIN32;NDEBUG;_CONSOLE"
+				PreprocessorDefinitions="ZSTD_MULTITHREAD=1;ZSTD_LEGACY_SUPPORT=0;WIN32;NDEBUG;_CONSOLE"
 				RuntimeLibrary="0"
 				EnableFunctionLevelLinking="true"
 				UsePrecompiledHeader="0"

build/VS2008/zstdlib/zstdlib.vcproj

@@ -45,7 +45,7 @@
 				Name="VCCLCompilerTool"
 				Optimization="0"
 				AdditionalIncludeDirectories="$(SolutionDir)..\..\lib;$(SolutionDir)..\..\lib\common;$(SolutionDir)..\..\lib\legacy;$(SolutionDir)..\..\programs\legacy;$(SolutionDir)..\..\lib\dictBuilder"
-				PreprocessorDefinitions="ZSTD_DLL_EXPORT=1;ZSTD_MULTITHREAD=1;ZSTD_LEGACY_SUPPORT=5;WIN32;_DEBUG;_CONSOLE"
+				PreprocessorDefinitions="ZSTD_DLL_EXPORT=1;ZSTD_MULTITHREAD=1;ZSTD_LEGACY_SUPPORT=0;WIN32;_DEBUG;_CONSOLE"
 				MinimalRebuild="true"
 				BasicRuntimeChecks="3"
 				RuntimeLibrary="3"
@@ -121,7 +121,7 @@
 				EnableIntrinsicFunctions="true"
 				OmitFramePointers="true"
 				AdditionalIncludeDirectories="$(SolutionDir)..\..\lib;$(SolutionDir)..\..\lib\common;$(SolutionDir)..\..\lib\legacy;$(SolutionDir)..\..\programs\legacy;$(SolutionDir)..\..\lib\dictBuilder"
-				PreprocessorDefinitions="ZSTD_DLL_EXPORT=1;ZSTD_MULTITHREAD=1;ZSTD_LEGACY_SUPPORT=5;WIN32;NDEBUG;_CONSOLE"
+				PreprocessorDefinitions="ZSTD_DLL_EXPORT=1;ZSTD_MULTITHREAD=1;ZSTD_LEGACY_SUPPORT=0;WIN32;NDEBUG;_CONSOLE"
 				RuntimeLibrary="0"
 				EnableFunctionLevelLinking="true"
 				UsePrecompiledHeader="0"
@@ -195,7 +195,7 @@
 				Name="VCCLCompilerTool"
 				Optimization="0"
 				AdditionalIncludeDirectories="$(SolutionDir)..\..\lib;$(SolutionDir)..\..\lib\common;$(SolutionDir)..\..\lib\legacy;$(SolutionDir)..\..\programs\legacy;$(SolutionDir)..\..\lib\dictBuilder"
-				PreprocessorDefinitions="ZSTD_DLL_EXPORT=1;ZSTD_MULTITHREAD=1;ZSTD_LEGACY_SUPPORT=5;WIN32;_DEBUG;_CONSOLE"
+				PreprocessorDefinitions="ZSTD_DLL_EXPORT=1;ZSTD_MULTITHREAD=1;ZSTD_LEGACY_SUPPORT=0;WIN32;_DEBUG;_CONSOLE"
 				MinimalRebuild="true"
 				BasicRuntimeChecks="3"
 				RuntimeLibrary="3"
@@ -272,7 +272,7 @@
 				EnableIntrinsicFunctions="true"
 				OmitFramePointers="true"
 				AdditionalIncludeDirectories="$(SolutionDir)..\..\lib;$(SolutionDir)..\..\lib\common;$(SolutionDir)..\..\lib\legacy;$(SolutionDir)..\..\programs\legacy;$(SolutionDir)..\..\lib\dictBuilder"
-				PreprocessorDefinitions="ZSTD_DLL_EXPORT=1;ZSTD_MULTITHREAD=1;ZSTD_LEGACY_SUPPORT=5;WIN32;NDEBUG;_CONSOLE"
+				PreprocessorDefinitions="ZSTD_DLL_EXPORT=1;ZSTD_MULTITHREAD=1;ZSTD_LEGACY_SUPPORT=0;WIN32;NDEBUG;_CONSOLE"
 				RuntimeLibrary="0"
 				EnableFunctionLevelLinking="true"
 				UsePrecompiledHeader="0"

build/VS2010/libzstd-dll/libzstd-dll.vcxproj

@@ -169,7 +169,7 @@
       </PrecompiledHeader>
       <WarningLevel>Level4</WarningLevel>
       <Optimization>Disabled</Optimization>
-      <PreprocessorDefinitions>ZSTD_DLL_EXPORT=1;ZSTD_MULTITHREAD=1;ZSTD_LEGACY_SUPPORT=5;WIN32;_DEBUG;_CONSOLE;_CRT_SECURE_NO_WARNINGS;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      <PreprocessorDefinitions>ZSTD_DLL_EXPORT=1;ZSTD_MULTITHREAD=1;ZSTD_LEGACY_SUPPORT=0;WIN32;_DEBUG;_CONSOLE;_CRT_SECURE_NO_WARNINGS;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <BasicRuntimeChecks>EnableFastChecks</BasicRuntimeChecks>
       <RuntimeLibrary>MultiThreadedDebugDLL</RuntimeLibrary>
       <DebugInformationFormat>EditAndContinue</DebugInformationFormat>
@@ -188,7 +188,7 @@
       </PrecompiledHeader>
       <WarningLevel>Level4</WarningLevel>
       <Optimization>Disabled</Optimization>
-      <PreprocessorDefinitions>ZSTD_DLL_EXPORT=1;ZSTD_MULTITHREAD=1;ZSTD_LEGACY_SUPPORT=5;WIN32;_DEBUG;_CONSOLE;_CRT_SECURE_NO_WARNINGS;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      <PreprocessorDefinitions>ZSTD_DLL_EXPORT=1;ZSTD_MULTITHREAD=1;ZSTD_LEGACY_SUPPORT=0;WIN32;_DEBUG;_CONSOLE;_CRT_SECURE_NO_WARNINGS;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <TreatWarningAsError>true</TreatWarningAsError>
       <BasicRuntimeChecks>EnableFastChecks</BasicRuntimeChecks>
       <RuntimeLibrary>MultiThreadedDebugDLL</RuntimeLibrary>
@@ -208,7 +208,7 @@
       <Optimization>MaxSpeed</Optimization>
       <FunctionLevelLinking>true</FunctionLevelLinking>
       <IntrinsicFunctions>true</IntrinsicFunctions>
-      <PreprocessorDefinitions>ZSTD_DLL_EXPORT=1;ZSTD_MULTITHREAD=1;ZSTD_LEGACY_SUPPORT=5;WIN32;NDEBUG;_CONSOLE;_CRT_SECURE_NO_WARNINGS;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      <PreprocessorDefinitions>ZSTD_DLL_EXPORT=1;ZSTD_MULTITHREAD=1;ZSTD_LEGACY_SUPPORT=0;WIN32;NDEBUG;_CONSOLE;_CRT_SECURE_NO_WARNINGS;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <EnablePREfast>false</EnablePREfast>
       <RuntimeLibrary>MultiThreaded</RuntimeLibrary>
       <DebugInformationFormat>ProgramDatabase</DebugInformationFormat>
@@ -229,7 +229,7 @@
       <Optimization>MaxSpeed</Optimization>
       <FunctionLevelLinking>true</FunctionLevelLinking>
       <IntrinsicFunctions>true</IntrinsicFunctions>
-      <PreprocessorDefinitions>ZSTD_DLL_EXPORT=1;ZSTD_MULTITHREAD=1;ZSTD_LEGACY_SUPPORT=5;WIN32;NDEBUG;_CONSOLE;_CRT_SECURE_NO_WARNINGS;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      <PreprocessorDefinitions>ZSTD_DLL_EXPORT=1;ZSTD_MULTITHREAD=1;ZSTD_LEGACY_SUPPORT=0;WIN32;NDEBUG;_CONSOLE;_CRT_SECURE_NO_WARNINGS;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <TreatWarningAsError>false</TreatWarningAsError>
       <EnablePREfast>false</EnablePREfast>
       <RuntimeLibrary>MultiThreaded</RuntimeLibrary>

build/VS2010/libzstd/libzstd.vcxproj

@@ -162,7 +162,7 @@
       </PrecompiledHeader>
       <WarningLevel>Level4</WarningLevel>
       <Optimization>Disabled</Optimization>
-      <PreprocessorDefinitions>ZSTD_MULTITHREAD=1;ZSTD_LEGACY_SUPPORT=5;WIN32;_DEBUG;_CONSOLE;_CRT_SECURE_NO_WARNINGS;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      <PreprocessorDefinitions>ZSTD_MULTITHREAD=1;ZSTD_LEGACY_SUPPORT=0;WIN32;_DEBUG;_CONSOLE;_CRT_SECURE_NO_WARNINGS;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <BasicRuntimeChecks>EnableFastChecks</BasicRuntimeChecks>
       <RuntimeLibrary>MultiThreadedDebugDLL</RuntimeLibrary>
       <DebugInformationFormat>EditAndContinue</DebugInformationFormat>
@@ -181,7 +181,7 @@
       </PrecompiledHeader>
       <WarningLevel>Level4</WarningLevel>
       <Optimization>Disabled</Optimization>
-      <PreprocessorDefinitions>ZSTD_MULTITHREAD=1;ZSTD_LEGACY_SUPPORT=5;WIN32;_DEBUG;_CONSOLE;_CRT_SECURE_NO_WARNINGS;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      <PreprocessorDefinitions>ZSTD_MULTITHREAD=1;ZSTD_LEGACY_SUPPORT=0;WIN32;_DEBUG;_CONSOLE;_CRT_SECURE_NO_WARNINGS;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <TreatWarningAsError>true</TreatWarningAsError>
       <BasicRuntimeChecks>EnableFastChecks</BasicRuntimeChecks>
       <RuntimeLibrary>MultiThreadedDebugDLL</RuntimeLibrary>
@@ -201,7 +201,7 @@
       <Optimization>MaxSpeed</Optimization>
       <FunctionLevelLinking>true</FunctionLevelLinking>
       <IntrinsicFunctions>true</IntrinsicFunctions>
-      <PreprocessorDefinitions>ZSTD_MULTITHREAD=1;ZSTD_LEGACY_SUPPORT=5;WIN32;NDEBUG;_CONSOLE;_CRT_SECURE_NO_WARNINGS;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      <PreprocessorDefinitions>ZSTD_MULTITHREAD=1;ZSTD_LEGACY_SUPPORT=0;WIN32;NDEBUG;_CONSOLE;_CRT_SECURE_NO_WARNINGS;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <EnablePREfast>false</EnablePREfast>
       <RuntimeLibrary>MultiThreaded</RuntimeLibrary>
       <DebugInformationFormat>ProgramDatabase</DebugInformationFormat>
@@ -222,7 +222,7 @@
       <Optimization>MaxSpeed</Optimization>
       <FunctionLevelLinking>true</FunctionLevelLinking>
       <IntrinsicFunctions>true</IntrinsicFunctions>
-      <PreprocessorDefinitions>ZSTD_MULTITHREAD=1;ZSTD_LEGACY_SUPPORT=5;WIN32;NDEBUG;_CONSOLE;_CRT_SECURE_NO_WARNINGS;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      <PreprocessorDefinitions>ZSTD_MULTITHREAD=1;ZSTD_LEGACY_SUPPORT=0;WIN32;NDEBUG;_CONSOLE;_CRT_SECURE_NO_WARNINGS;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <TreatWarningAsError>false</TreatWarningAsError>
       <EnablePREfast>false</EnablePREfast>
       <RuntimeLibrary>MultiThreaded</RuntimeLibrary>

build/VS2010/zstd/zstd.vcxproj

@@ -187,7 +187,7 @@
       </PrecompiledHeader>
       <WarningLevel>Level4</WarningLevel>
       <Optimization>Disabled</Optimization>
-      <PreprocessorDefinitions>ZSTD_MULTITHREAD=1;ZSTD_LEGACY_SUPPORT=5;WIN32;_DEBUG;_CONSOLE;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      <PreprocessorDefinitions>ZSTD_MULTITHREAD=1;ZSTD_LEGACY_SUPPORT=0;WIN32;_DEBUG;_CONSOLE;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <TreatWarningAsError>true</TreatWarningAsError>
       <EnablePREfast>false</EnablePREfast>
       <EnableEnhancedInstructionSet>$(InstructionSet)</EnableEnhancedInstructionSet>
@@ -204,7 +204,7 @@
       </PrecompiledHeader>
       <WarningLevel>Level4</WarningLevel>
       <Optimization>Disabled</Optimization>
-      <PreprocessorDefinitions>ZSTD_MULTITHREAD=1;ZSTD_LEGACY_SUPPORT=5;WIN32;_DEBUG;_CONSOLE;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      <PreprocessorDefinitions>ZSTD_MULTITHREAD=1;ZSTD_LEGACY_SUPPORT=0;WIN32;_DEBUG;_CONSOLE;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <TreatWarningAsError>true</TreatWarningAsError>
       <EnablePREfast>false</EnablePREfast>
       <EnableEnhancedInstructionSet>$(InstructionSet)</EnableEnhancedInstructionSet>
@@ -223,7 +223,7 @@
       <Optimization>MaxSpeed</Optimization>
       <FunctionLevelLinking>true</FunctionLevelLinking>
       <IntrinsicFunctions>true</IntrinsicFunctions>
-      <PreprocessorDefinitions>ZSTD_MULTITHREAD=1;ZSTD_LEGACY_SUPPORT=5;WIN32;NDEBUG;_CONSOLE;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      <PreprocessorDefinitions>ZSTD_MULTITHREAD=1;ZSTD_LEGACY_SUPPORT=0;WIN32;NDEBUG;_CONSOLE;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <EnablePREfast>false</EnablePREfast>
       <TreatWarningAsError>false</TreatWarningAsError>
       <RuntimeLibrary>MultiThreaded</RuntimeLibrary>
@@ -245,7 +245,7 @@
       <Optimization>MaxSpeed</Optimization>
       <FunctionLevelLinking>true</FunctionLevelLinking>
       <IntrinsicFunctions>true</IntrinsicFunctions>
-      <PreprocessorDefinitions>ZSTD_MULTITHREAD=1;ZSTD_LEGACY_SUPPORT=5;WIN32;NDEBUG;_CONSOLE;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      <PreprocessorDefinitions>ZSTD_MULTITHREAD=1;ZSTD_LEGACY_SUPPORT=0;WIN32;NDEBUG;_CONSOLE;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <TreatWarningAsError>false</TreatWarningAsError>
       <EnablePREfast>false</EnablePREfast>
       <RuntimeLibrary>MultiThreaded</RuntimeLibrary>

build/cmake/CMakeModules/ZstdOptions.cmake

@@ -2,8 +2,8 @@
 # ZSTD Build Options Configuration
 # ################################################################
 
-# Legacy support configuration
-option(ZSTD_LEGACY_SUPPORT "Enable legacy format support" ON)
+# Legacy support configuration (disabled by default)
+option(ZSTD_LEGACY_SUPPORT "Enable legacy format support" OFF)
 
 if(ZSTD_LEGACY_SUPPORT)
     message(STATUS "ZSTD_LEGACY_SUPPORT enabled")

build/meson/meson_options.txt

@@ -10,8 +10,8 @@
 
 # Read guidelines from https://wiki.gnome.org/Initiatives/GnomeGoals/MesonPorting
 
-option('legacy_level', type: 'integer', min: 0, max: 7, value: 5,
-  description: 'Support any legacy format: 7 to 1 for v0.7+ to v0.1+')
+option('legacy_level', type: 'integer', min: 0, max: 7, value: 0,
+  description: 'Support legacy format: 0=disabled, 1-7=support v0.1+ to v0.7+')
 option('debug_level', type: 'integer', min: 0, max: 9, value: 1,
   description: 'Enable run-time debug. See lib/common/debug.h')
 option('backtrace', type: 'feature', value: 'disabled',

lib/BUCK

@@ -57,7 +57,7 @@ cxx_library(
     srcs=glob(['legacy/*.c']),
     deps=[':common'],
     exported_preprocessor_flags=[
-        '-DZSTD_LEGACY_SUPPORT=4',
+        '-DZSTD_LEGACY_SUPPORT=0',
     ],
 )
 

lib/README.md

@@ -12,8 +12,9 @@ including commands variables, staged install, directory variables and standard t
 - `make` : generates both static and dynamic libraries
 - `make install` : install libraries, headers and pkg-config in local system directories
 
-`libzstd` default scope is extensive, including compression, decompression, dictionary builder,
-and support for decoding legacy formats >= v0.5.0 by default.
+`libzstd` default scope includes compression, decompression, and dictionary builder.
+Note: starting v1.6.0, support for decoding legacy formats is disabled by default.
+See _modular build_ below to learn how to enable it.
 The scope can be reduced on demand (see paragraph _modular build_).
 
 #### Multiarch Support
@@ -99,7 +100,7 @@ The file structure is designed to make this selection manually achievable for an
         Specifying a number limits versions supported to that version onward.
         For example, `ZSTD_LEGACY_SUPPORT=2` means : "support legacy formats >= v0.2.0".
         Conversely, `ZSTD_LEGACY_SUPPORT=0` means "do __not__ support legacy formats".
-        By default, this build macro is set as `ZSTD_LEGACY_SUPPORT=5`.
+        By default, this build macro is set as `ZSTD_LEGACY_SUPPORT=0` (disabled).
         Decoding supported legacy format is a transparent capability triggered within decompression functions.
         It's also allowed to invoke legacy API directly, exposed in `lib/legacy/zstd_legacy.h`.
         Each version does also provide its own set of advanced API.

lib/libzstd.mk

@@ -28,12 +28,8 @@ LIB_BINDIR ?= $(LIB_SRCDIR)
 # configures a bunch of other variables to space-optimized defaults.
 ZSTD_LIB_MINIFY ?= 0
 
-# Legacy support
-ifneq ($(ZSTD_LIB_MINIFY), 0)
-  ZSTD_LEGACY_SUPPORT ?= 0
-else
-  ZSTD_LEGACY_SUPPORT ?= 5
-endif
+# Legacy support disabled by default
+ZSTD_LEGACY_SUPPORT ?= 0
 ZSTD_LEGACY_MULTITHREADED_API ?= 0
 
 # Build size optimizations

lib/zstd.h

@@ -110,8 +110,8 @@ extern "C" {
 
 /*------   Version   ------*/
 #define ZSTD_VERSION_MAJOR    1
-#define ZSTD_VERSION_MINOR    5
-#define ZSTD_VERSION_RELEASE  8
+#define ZSTD_VERSION_MINOR    6
+#define ZSTD_VERSION_RELEASE  0
 #define ZSTD_VERSION_NUMBER  (ZSTD_VERSION_MAJOR *100*100 + ZSTD_VERSION_MINOR *100 + ZSTD_VERSION_RELEASE)
 
 /*! ZSTD_versionNumber() :

tests/Makefile

@@ -20,7 +20,7 @@
 # zstreamtest32: Same as zstreamtest, but forced to compile in 32-bits mode
 # ##########################################################################
 
-ZSTD_LEGACY_SUPPORT ?= 5
+ZSTD_LEGACY_SUPPORT ?= 0
 export ZSTD_LEGACY_SUPPORT
 
 DEBUGLEVEL ?= 2

tests/libzstd_builds.sh

@@ -21,14 +21,14 @@ mustBeAbsent() {
     $ECHO "$@ correctly not present"  # for some reason, this $ECHO must exist, otherwise mustBeAbsent() always fails (??)
 }
 
-# default compilation : all features enabled - no zbuff
+# default compilation : all features enabled - no zbuff, no legacy
 $ECHO "testing default library compilation"
 CFLAGS= make -C $DIR/../lib libzstd libzstd.a > $INTOVOID
 nm $DIR/../lib/libzstd.a | $GREP "\.o" > tmplog
 isPresent "zstd_compress.o"
 isPresent "zstd_decompress.o"
 isPresent "zdict.o"
-isPresent "zstd_v07.o"
+mustBeAbsent "zstd_v07.o"
 mustBeAbsent "zbuff_compress.o"
 $RM tmplog
 
@@ -44,7 +44,7 @@ nm $DIR/../lib/libzstd.a | $GREP "\.o" > tmplog
 mustBeAbsent "zstd_compress.o"
 isPresent "zstd_decompress.o"
 mustBeAbsent "zdict.o"
-isPresent "zstd_v07.o"
+mustBeAbsent "zstd_v07.o"
 mustBeAbsent "zbuff_compress.o"
 $RM $DIR/../lib/libzstd.a tmplog
 
@@ -66,7 +66,7 @@ nm $DIR/../lib/libzstd.a | $GREP "\.o" > tmplog
 isPresent "zstd_compress.o"
 isPresent "zstd_decompress.o"
 isPresent "zdict.o"
-isPresent "zstd_v07.o"
+mustBeAbsent "zstd_v07.o"
 mustBeAbsent "zbuff_compress.o"
 $RM $DIR/../lib/libzstd.a tmplog
 
@@ -77,7 +77,7 @@ nm $DIR/../lib/libzstd.a | $GREP "\.o" > tmplog
 isPresent "zstd_compress.o"
 isPresent "zstd_decompress.o"
 isPresent "zdict.o"
-isPresent "zstd_v07.o"
+mustBeAbsent "zstd_v07.o"
 isPresent "zbuff_compress.o"
 $RM $DIR/../lib/libzstd.a tmplog
 
@@ -88,7 +88,7 @@ nm $DIR/../lib/libzstd.a | $GREP "\.o" > tmplog
 isPresent "zstd_compress.o"
 isPresent "zstd_decompress.o"
 mustBeAbsent "zdict.o"
-isPresent "zstd_v07.o"
+mustBeAbsent "zstd_v07.o"
 mustBeAbsent "zbuff_compress.o"
 $RM $DIR/../lib/libzstd.a tmplog
 
@@ -102,3 +102,14 @@ mustBeAbsent "zdict.o"
 mustBeAbsent "zstd_v07.o"
 mustBeAbsent "zbuff_compress.o"
 $RM $DIR/../lib/libzstd.a tmplog
+
+# legacy support explicitly enabled
+$ECHO "testing with legacy support explicitly enabled"
+ZSTD_LEGACY_SUPPORT=5 CFLAGS= make -C $DIR/../lib libzstd.a > $INTOVOID
+nm $DIR/../lib/libzstd.a | $GREP "\.o" > tmplog
+isPresent "zstd_compress.o"
+isPresent "zstd_decompress.o"
+isPresent "zdict.o"
+isPresent "zstd_v07.o"
+mustBeAbsent "zbuff_compress.o"
+$RM $DIR/../lib/libzstd.a tmplog

tests/test-zstd-versions.py

@@ -259,13 +259,23 @@ def decompress_dict(tag):
                     shutil.copy2('dictBuilder', '{}/dictBuilder.{}'.format(tmp_dir, tag))
                 os.chdir(r_dir + '/programs')  # /path/to/zstd/tests/versionsTest/<TAG>/programs
                 make(['clean'], False)  # separate 'clean' target to allow parallel build
-                make(['zstd'], False)
+                # Enable legacy support for cross-version compatibility testing.
+                # Use ZSTD_LEGACY_SUPPORT=1 for v0.6.x due to a bug where headers
+                # check for ==1 but code checks for >=1.
+                # Use ZSTD_LEGACY_SUPPORT=5 for v1.2.0+ because =1 includes old
+                # legacy files (v01-v04) that have missing includes in newer versions.
+                if tag < 'v1.2.0':
+                    make(['zstd', 'ZSTD_LEGACY_SUPPORT=1'], False)
+                else:
+                    make(['zstd', 'ZSTD_LEGACY_SUPPORT=5'], False)
             else:
                 os.chdir(programs_dir)
                 print('-----------------------------------------------')
                 print('compiling head')
                 print('-----------------------------------------------')
-                make(['zstd'], False)
+                # Enable legacy support for head to test cross-version compatibility
+                # (legacy support is disabled by default since v1.6.0)
+                make(['zstd', 'ZSTD_LEGACY_SUPPORT=5'], False)
             shutil.copy2('zstd', dst_zstd)
 
     # remove any remaining *.zst and *.dec from previous test