<AWT Dev> RFR: JDK-8200178 Remove mapfiles for JDK native libraries

Magnus Ihse Bursie magnus.ihse.bursie at oracle.com
Fri Mar 23 20:36:29 UTC 2018

On 2018-03-23 19:01, Phil Race wrote:
> http://cr.openjdk.java.net/~ihse/JDK-8200178-remove-mapfiles/webrev.01/src/java.desktop/share/native/libmlib_image/mlib_image_proto.h.udiff.html 
> The variable definitions here are now misaligned.
No, they are not. That's just an artifact of webrev, which filters out 
whitespace changes in the diff view. :-( To see the proper changes, 
including whitespace, you need to download the patch file.

I've gone to great pains to mimick the existing style in the source 
codes I've made changes to.


> ..and added 2d-dev since many of these native changes are in 2d.
> -phil.
> On 03/23/2018 10:33 AM, Phil Race wrote:
>> There are a lot of changes in the desktop libraries.
>> Doing mach5 tier1/2/3 testing is not nearly sufficient to cover those 
>> since
>> only tier3 has any UI tests and it barely uses anything that's 
>> touched here.
>> So since testing seems to be wise, then I think you should do a
>> jtreg desktop group run on Linux & Windows.
>> You can probably skip Mac since it is unaffected and I think Linux 
>> will cover Solaris here.
>> You should also do some headless testing.
>> It could take some time to review this properly and decide what 
>> changes are OK,
>> what changes are something we should clean up later, and what changes 
>> are something
>> that ought to be addressed now ..
>> I think I'd be mainly concerned that something fails due to a missing 
>> symbol, or
>> that for newly exported symbols if we ended up with duplicate symbols 
>> as a result.
>> The results of a test run will add confidence here.
>> BTW I don't think you are right that
>> java.desktop:/libawt_headless: The following symbols are now also 
>> exported due to JNIEXPORT (they were previously
>> ..
>>  X11SurfaceData_GetOps
>> It looks to me like it was previously exported.
>> -phil.
>> On 03/23/2018 06:56 AM, Magnus Ihse Bursie wrote:
>>> With modern compilers, we can use compiler directives (such as 
>>> _attribute__((visibility("default"))), or __declspec(dllexport)) to 
>>> control symbol visibility, directly in the source code. This has 
>>> historically not been present on all compilers, so we had to resort 
>>> to using mapfiles (also known as linker scripts).
>>> This is no longer the case. Now all compilers we use support symbol 
>>> visibility directives, in one form or another. We should start using 
>>> this. Since this has been the only way to control symbol visibility 
>>> on Windows, for most of the shared code, we already have proper 
>>> JNIEXPORT decorations in place.
>>> If we fix the remaining platform-specific files to have proper 
>>> JNIEXPORT tagging, then we can finally get rid of mapfiles.
>>> This fix removed mapfiles for all JDK libraries. It does not touch 
>>> hotspot libraries nor JDK executables; they will have to wait for a 
>>> future fix -- this was complex enough. This change will not have any 
>>> impact on macosx, since we do not use mapfiles there, but instead 
>>> export all symbols. (This is not a good idea, but I'll address that 
>>> separately.) This change will also have a minimal impact on Windows. 
>>> The only reason Windows is impacted at all, is that some changes 
>>> needed by Solaris and Linux were simpler to fix for all platforms.
>>> I have strived for this change to have no impact on the actual 
>>> generated code. Unfortunately, this was not possible to fully 
>>> achieve. I do not believe that these changes will have any actual 
>>> impact on the product, though. I will present the differences more 
>>> in detail further down. Those who are not interested can probably 
>>> skip that.
>>> The patch has passed tier1 testing and is currently running tier2 
>>> and tier3. Since the running code is more or less (see caveat below) 
>>> unmodified, I don't expect any testing issues.
>>> Bug: https://bugs.openjdk.java.net/browse/JDK-8200178
>>> WebRev: 
>>> http://cr.openjdk.java.net/~ihse/JDK-8200178-remove-mapfiles/webrev.01
>>> Details on changes:
>>> Most of the source code changes are (unsurprisingly) in java.base 
>>> and java.desktop. Remaining changes are in jdk.crypto.ucrypto, 
>>> jdk.hotspot.agent, jdk.jdi and jdk.jdwp.agent.
>>> Source code changes does almost to 100% consists in decorating an 
>>> exported function with JNIEXPORT. I have also followed the 
>>> long-standing convention of adding JNICALL. This is a no-op on 
>>> non-Windows platforms, so for most of the changes this is purely 
>>> cosmetic (and possibly adding in robustness, should the function 
>>> ever be used on Windows in the future). I have also followed the 
>>> stylistic convention of putting "JNIEXPORT <return type> JNICALL" on 
>>> a separate line. For some functions, however, this might cause a 
>>> change in calling convention on Windows. Since this can not apply to 
>>> exported functions on Windows (otherwise they would already have had 
>>> JNIEXPORT), I do not think this matters anything.
>>> A few libraries did not have a mapfile, on Linux and/or Solaris. 
>>> This actually meant that all symbols were exported. It is highly 
>>> unclear if this was known and intended by the original make rule 
>>> writer. I have emulated this by adding the flag 
>>> $(EXPORT_ALL_SYMBOLS) to these libraries. Hopefully, we can remove 
>>> this flag and fix proper exported symbols in the future.
>>> I have run the complete build using COMPARE_BUILD, and made a 
>>> thourough analysis of the differences for Linux and Solaris. All 
>>> native libraries have symbol differences, but most of them are 
>>> trivial and/or harmless. As a result, most libraries have disasm 
>>> differences as well, but these too seem trivial and harmless. The 
>>> differences in symbols that are common to all libraries include:
>>>  * Internal symbols such as __bss_start, _edata, _end and _fini are 
>>> now global. (They are imported as such from the compiler 
>>> libraries/archives, and we have no linker script to override this 
>>> behavior).
>>>  * The versioning tag SUNWprivate_1.1 is not included, and thus 
>>> neither the .gnu.version_d symbol.
>>>  * There are a few differences in the symbol and/or mangling of some 
>>> local functions. I'm not sure what's causing this,
>>> but it's unlikely to have any effect on the product.
>>> Another common source for change in symbols is due to previous 
>>> platform differences. For instance, if we had "JNIEXPORT int JNICALL 
>>> do_foo() { ... }", but do_foo was not in the mapfile, the symbol was 
>>> exported on Windows but not on Linux and Solaris. (Presumable since 
>>> it was not needed there, even though it was compiled for those 
>>> platforms as well.) Now, with the mapfiles gone, do_foo() will be 
>>> exported on all platforms. And contrary, functions that are compiled 
>>> on all platforms, and were exported in mapfiles, but now have gotten 
>>> an JNIEXPORT decoration, will now be visible even on Windows. (This 
>>> accounts for half of the noticed symbol differences on Windows.) I 
>>> could have made the JNIEXPORT conditional on OS, but I didn't think 
>>> the mess in source code were worth the keeping of binary confidence 
>>> with the old build.
>>> A third common source for change in symbols is due to exported 
>>> functions "leaking" across library borders. For instance, some 
>>> functions in java.desktop is compiled in both libawt_xawt and 
>>> libawt_headless, but they were previously only included in the 
>>> mapfile for one of these libraries. Now, since the visibility is 
>>> determined by the source code itself, it gets exported in both 
>>> libraries. A variant of this is when a library depends on another 
>>> JDK library, and includes the header file from that other library, 
>>> which in turn declares a function as JNIEXPORT. This will cause the 
>>> including library to also export the function. This accounts for the 
>>> other half of the changes on Windows. A typical example of this is 
>>> that multiple libraries now re-export hotspot symbols from 
>>> libjvm.so, like jio_fprintf. (I have not listed the libjvm 
>>> re-exports below.)
>>> Note that  Java_java_io_FileOutputStream_close0 in 
>>> java.base/unix/native/libjava/FileOutputStream_md.c is no longer 
>>> exported,
>>> and can probably be removed.
>>> Here is a detailed table showing and accounting for all the 
>>> remaining differences found on Linux and Solaris:
>>> java.base/unix/native/libjava: Java_java_io_FileOutputStream_close0 
>>> is now also exported on unix platforms due to JNIEXPORT.
>>> java.base/jspawnlauncher: On solaris, we also include 
>>> libjava/childproc.o, which
>>> now exports less functions than it used to (it used to export all 
>>> functions, now it is compiled with visibility=hidden).
>>> java.base/java(w).exe: Is now also exporting the following symbols 
>>> due to added JNIEXPORT in libjli on Windows:
>>> (Yes, executables can export symbols on Windows. Confusing, I know.)
>>>  JLI_AddArgsFromEnvVar
>>>  JLI_CmdToArgs
>>>  JLI_GetAppArgIndex
>>>  JLI_GetStdArgc
>>>  JLI_GetStdArgs
>>>  JLI_InitArgProcessing
>>>  JLI_Launch
>>>  JLI_List_add
>>>  JLI_List_new
>>>  JLI_ManifestIterate
>>>  JLI_MemAlloc
>>>  JLI_MemFree
>>>  JLI_PreprocessArg
>>>  JLI_ReportErrorMessage
>>>  JLI_ReportErrorMessageSys
>>>  JLI_ReportExceptionDescription
>>>  JLI_ReportMessage
>>>  JLI_SetTraceLauncher
>>>  JLI_StringDup
>>> java.desktop:/libawt_xawt: The following symbols are now also 
>>> exported on linux and solaris due to JNIEXPORT:
>>>  awt_DrawingSurface_FreeDrawingSurfaceInfo
>>>  awt_DrawingSurface_GetDrawingSurfaceInfo
>>>  awt_DrawingSurface_Lock
>>>  awt_DrawingSurface_Unlock
>>>  awt_GetColor
>>> The following symbols are now also exported on linux and solaris due 
>>> to JNIEXPORT (they were previously
>>>  exported only in libawt):
>>>  Java_sun_awt_DebugSettings_setCTracingOn__Z
>>>  Java_sun_awt_DebugSettings_setCTracingOn__ZLjava_lang_String_2
>>>  Java_sun_awt_DebugSettings_setCTracingOn__ZLjava_lang_String_2I
>>>  Java_sun_awt_X11GraphicsConfig_getNumColors
>>> java.desktop:/libawt_headless: The following symbols are now also 
>>> exported due to JNIEXPORT (they were previously
>>>  exported only in libawt_xawt and/or libawt):
>>>  Java_sun_java2d_opengl_GLXGraphicsConfig_getGLXConfigInfo
>>>  Java_sun_java2d_opengl_GLXGraphicsConfig_getOGLCapabilities
>>>  Java_sun_java2d_x11_X11PMBlitLoops_updateBitmask
>>>  Java_sun_java2d_x11_X11SurfaceData_isShmPMAvailable
>>>  X11SurfaceData_GetOps
>>> java.desktop/libawt: The following symbols are now also exported on 
>>> Windows, due to added
>>>  SurfaceData_InitOps
>>>  mul8table
>>>  div8table
>>>  doDrawPath
>>>  doFillPath
>>>  g_CMpDataID
>>>  initInverseGrayLut
>>>  make_dither_arrays
>>>  make_uns_ordered_dither_array
>>>  path2DFloatCoordsID
>>>  path2DNumTypesID
>>>  path2DTypesID
>>>  path2DWindingRuleID
>>>  sg2dStrokeHintID
>>>  std_img_oda_blue
>>>  std_img_oda_green
>>>  std_img_oda_red
>>>  std_odas_computed
>>> java.desktop/libawt on solaris:
>>> A number of "#pragma weak" directives was previously overridden by 
>>> the mapfile.
>>> Now these directives are respected, so these symbols are now weak 
>>> instead of local:
>>>  ByteGrayToIntArgbPreConvert_F
>>>  ByteGrayToIntArgbPreScaleConvert_F
>>>  IntArgbBmToFourByteAbgrPreScaleXparOver_F
>>>  IntArgbToIntRgbXorBlit_F
>>>  IntBgrToIntBgrAlphaMaskBlit_F
>>> java.desktop/libawt on solaris: These are now also exported due to 
>>> JNIEXPORT in libmlib_image.
>>>  j2d_mlib_ImageCreate
>>>  j2d_mlib_ImageCreateStruct
>>>  j2d_mlib_ImageDelete
>>> java.desktop/libawt on solaris: This is now also exported due to 
>>>  GrPrim_CompGetXorColor
>>>  SurfaceData_GetOpsNoSetup
>>>  SurfaceData_IntersectBoundsXYWH
>>>  SurfaceData_SetOps
>>>  Transform_GetInfo
>>>  Transform_transform
>>> java.desktop/libsplashscreen: JNI_OnLoad is now exported on linux 
>>> and solaris due to JNIEXPORT.
>>> libspashscreen also had JNIEXPORT (actually a pure 
>>> _declspec(dllexport)) but no JNICALL, which I added as
>>> a part of converting to JNIEXPORT. The same goes for libmlib_image .
>>> jdk.sctp/libsctp: handleSocketError is now exported on linux and 
>>> solaris due to JNIEXPORT in libnio.
>>> java.instrument:/libinstrument: Agent_OnUnload is now also exported 
>>> on linux and solaris platforms due to JNIEXPORT.
>>> JLI_ManifestIterate is now also exported on Windows, due to added 
>>> JNIEXPORT in libjli.
>>> jdk.management/libmanagement_ext: 
>>> Java_com_sun_management_internal_Flag_setDoubleValue is now also 
>>> exported on linux and solaris platforms due to JNIEXPORT.
>>> /Magnus

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