I have been asked in bug #86958 to open a separate bug about the resolution of the compilation error reported there, where mesa is compiled against llvm>=3.6.
To fix that compilation error, at line 504 of file lp_bld_misc.cpp the ShaderMemoryManager* object MM is passed to a unique_ptr object, which takes ownership of MM. However, in the event of the call to EngineBuilder::create() at line 523 failing, at line 530 delete is called manually on MM, thus leading to a possible double delete (since the destructor of the unique_ptr object having ownership will also attempt to delete MM).
This may beg the question of what EngineBuilder::setMCJITMemoryManager(ShaderMemoryManager*) does in llvm < 3.6. If that method also tries to delete its argument when finished with, you would get a double delete in the error case (ie where EngineBuilder::create() fails) for earlier versions of llvm also. However, whatever the answer to that, the fix for bug 86958 is on the fact of it wrong.
Would this fix it?
diff --git a/src/gallium/auxiliary/gallivm/lp_bld_misc.cpp b/src/gallium/auxiliary/gallivm/lp_bld_misc.cpp
index 5210acc..7387ffb 100644
@@ -502,6 +502,7 @@ lp_build_create_jit_compiler_for_module(LLVMExecutionEngineRef *OutJIT,
#if HAVE_LLVM >= 0x0306
+ MM = NULL;
That will work fine.
This does beg the question whether the code is correct for llvm < 3.6 (it fixes llvm >= 3.6).
(In reply to Chris Vine from comment #2)
> That will work fine.
> This does beg the question whether the code is correct for llvm < 3.6 (it
> fixes llvm >= 3.6).
I believe so.
LLVM 3.4 and 3.3's documentation for setMCJITMemoryManager/setJITMemoryManager state they only take onwership if builder.create() is successful.
And indeed we only delete MM when builder.create() fails.
Fixed on http://cgit.freedesktop.org/mesa/mesa/commit/?id=70dc8a9930f561d7ce6db7e58b5bc9b4d940e37b
on Feb 25, 2017 at 20:36:11.
(provided by the Example extension).