Re: devel/llvm90 requires math/z3 first; building math/z3 requires a c++ toolchain be in place

[Mark Millard via freebsd-toolchain]

On 2019-Aug-7, at 12:56, Brooks Davis <brooks at freebsd.org> wrote:

> On Wed, Aug 07, 2019 at 11:55:04AM -0700, Mark Millard wrote:
>> 
>> 
>> On 2019-Aug-7, at 11:02, Brooks Davis <brooks at freebsd.org> wrote:
>> 
>>> On Wed, Aug 07, 2019 at 05:17:14PM +0000, Brooks Davis wrote:
>>>> On Tue, Aug 06, 2019 at 09:22:52PM -0700, Mark Millard wrote:
>>>>> [I found something known to be missing in the
>>>>> in at least some versions of
>>>>> llvm/cmake/modules/CrossCompile.cmake that messes
>>>>> up the overall handling of LLVM_ENABLE_Z3_SOLVER .]
>>>>> 
>>>>> On 2019-Aug-6, at 20:23, Mark Millard <marklmi at yahoo.com> wrote:
>>>>> 
>>>>> 
>>>>> 
>>>>>> On 2019-Aug-6, at 19:08, Brooks Davis <brooks at freebsd.org> wrote:
>>>>>> 
>>>>>>> On Tue, Aug 06, 2019 at 05:59:21PM -0700, Mark Millard wrote:
>>>>>>>> 
>>>>>>>> 
>>>>>>>> On 2019-Aug-6, at 09:55, Brooks Davis <brooks at freebsd.org> wrote:
>>>>>>>> 
>>>>>>>>> I'd prefer to disable this dependency.  There's a knob that worked in
>>>>>>>>> the 8.0 timeframe, but the lit build now autodetects z3 when it is
>>>>>>>>> present and I've failed to find a knob to disable it.  For now, the 
>>>>>>>>> easy
>>>>>>>>> workaround is probably to disable options LIT.  We could make that the
>>>>>>>>> default on non-LLVM platforms is that makes sense.
>>>>>>>>> 
>>>>>>>>> -- Brooks
>>>>>>>> 
>>>>>>>> Okay.
>>>>>>>> 
>>>>>>>> poudriere-devel automatically built math/z3 because
>>>>>>>> I'd indicated to build devel/llvm90 . math/z3 was not
>>>>>>>> previously built: I've never had other use of it. So
>>>>>>>> my context was not one of an implicit autodetect.
>>>>>>> 
>>>>>>> The dependency is there because if z3 is installed then the package
>>>>>>> that is built depends on z3.  Thus I had not choice but to add a z3
>>>>>>> dependency until I find a way to turn it off.  You can either help find
>>>>>>> a way to disable z3 detection in the cmake infrastructure or turn off
>>>>>>> LIT.  I don't have any use for reports on the effects of commenting out
>>>>>>> the DEPENDS line.  I know what that does.
>>>>>> 
>>>>>> 
>>>>>> I hope this helps. (I'm not a cmake expert.)
>>>>>> 
>>>>>> llvm-9.0.0rc1.src/lib/Support/Z3Solver.cpp does:
>>>>>> 
>>>>>> #if LLVM_WITH_Z3
>>>>>> 
>>>>>> #include <z3.h>
>>>>>> 
>>>>>> namespace {
>>>>>> . . .
>>>>>> } // end anonymous namespace
>>>>>> 
>>>>>> #endif
>>>>>> 
>>>>>> llvm::SMTSolverRef llvm::CreateZ3Solver() {
>>>>>> #if LLVM_WITH_Z3
>>>>>> return llvm::make_unique<Z3Solver>();
>>>>>> #else
>>>>>> llvm::report_fatal_error("LLVM was not compiled with Z3 support, rebuild 
>>>>>> "
>>>>>>                         "with -DLLVM_ENABLE_Z3_SOLVER=ON",
>>>>>>                         false);
>>>>>> return nullptr;
>>>>>> #endif
>>>>>> }
>>>>>> 
>>>>>> (There are other places LLVM_WITH_Z3 is used but the
>>>>>> above is suggestive.)
>>>>>> 
>>>>>> Working backwards finds that:
>>>>>> 
>>>>>> /wrkdirs/usr/ports/devel/llvm90/work/llvm-9.0.0rc1.src/CMakeLists.txt
>>>>>> 
>>>>>> shows LLVM_WITH_Z3 being conditionally set to 1 via . . .
>>>>>> 
>>>>>> set(LLVM_Z3_INSTALL_DIR "" CACHE STRING "Install directory of the Z3 
>>>>>> solver.")
>>>>>> 
>>>>>> find_package(Z3 4.7.1)
>>>>>> 
>>>>>> if (LLVM_Z3_INSTALL_DIR)
>>>>>> if (NOT Z3_FOUND)
>>>>>>  message(FATAL_ERROR "Z3 >= 4.7.1 has not been found in 
>>>>>> LLVM_Z3_INSTALL_DIR: ${LLVM_Z3_INSTALL_DIR}.")
>>>>>> endif()
>>>>>> endif()
>>>>>> 
>>>>>> set(LLVM_ENABLE_Z3_SOLVER_DEFAULT "${Z3_FOUND}")
>>>>>> 
>>>>>> option(LLVM_ENABLE_Z3_SOLVER
>>>>>> "Enable Support for the Z3 constraint solver in LLVM."
>>>>>> ${LLVM_ENABLE_Z3_SOLVER_DEFAULT}
>>>>>> )
>>>>>> 
>>>>>> if (LLVM_ENABLE_Z3_SOLVER)
>>>>>> if (NOT Z3_FOUND)
>>>>>>  message(FATAL_ERROR "LLVM_ENABLE_Z3_SOLVER cannot be enabled when Z3 is 
>>>>>> not available.")
>>>>>> endif()
>>>>>> 
>>>>>> set(LLVM_WITH_Z3 1)
>>>>>> endif()
>>>>>> 
>>>>>> if( LLVM_TARGETS_TO_BUILD STREQUAL "all" )
>>>>>> set( LLVM_TARGETS_TO_BUILD ${LLVM_ALL_TARGETS} )
>>>>>> endif()
>>>>>> 
>>>>>> 
>>>>>> If I read that correctly, LLVM_ENABLE_Z3_SOLVER set directly
>>>>>> appears to override the default (that tracks if z3 was found).
>>>>> 
>>>>> I saw a reference to:
>>>>> 
>>>>> diff --git a/llvm/cmake/modules/CrossCompile.cmake 
>>>>> b/llvm/cmake/modules/CrossCompile.cmake
>>>>> index bc3b210f018..0c30b88f80f 100644
>>>>> --- a/llvm/cmake/modules/CrossCompile.cmake
>>>>> +++ b/llvm/cmake/modules/CrossCompile.cmake
>>>>> @@ -53,6 +53,7 @@ function(llvm_create_cross_target_internal target_name 
>>>>> toolchain buildtype)
>>>>>        -DLLVM_DEFAULT_TARGET_TRIPLE="${TARGET_TRIPLE}"
>>>>>        -DLLVM_TARGET_ARCH="${LLVM_TARGET_ARCH}"
>>>>>        
>>>>> -DLLVM_TEMPORARILY_ALLOW_OLD_TOOLCHAIN="${LLVM_TEMPORARILY_ALLOW_OLD_TOOLCHAIN}"
>>>>> +        -DLLVM_ENABLE_Z3_SOLVER="${LLVM_ENABLE_Z3_SOLVER}"
>>>>>        ${build_type_flags} ${linker_flag} ${external_clang_dir}
>>>>>    WORKING_DIRECTORY ${LLVM_${target_name}_BUILD}
>>>>>    DEPENDS CREATE_LLVM_${target_name}
>>>>> 
>>>>> in https://reviews.llvm.org/D54978 on Feb 12 2019, 5:41 PM
>>>>> and it had the comment:
>>>>> 
>>>>> QUOTE
>>>>> Independent of the rest of the discussion, this patch should be part of 
>>>>> the reland, to make sure that explicitly turning off Z3 works reliably. 
>>>>> Thanks for coming up with that, and thanks everyone for the good 
>>>>> discussion here :)
>>>>> END QUOTE
>>>>> 
>>>>> This apparently fixes a sub-cmake not respecting the
>>>>> LLVM_ENABLE_Z3_SOLVER setting in the parent cmake.
>>>>> (The overall review earlier describes the sub-cmake
>>>>> not doing the right thing.)
>>>> 
>>>> Thanks for digging this up.  Unfortunately, this doesn't seem to have
>>>> solved the problem.  With this patch applied I still get this if I have
>>>> z3 installed on the system and no LIB_DEPENDS line:
>>>> 
>>>> Error: /usr/local/bin/FileCheck90 is linked to /usr/local/lib/libz3.so.0
>>>> from math/z3 but it is not declared as a dependency
>>>> Warning: you need LIB_DEPENDS+=libz3.so:math/z3
>>>> 
>>>> I've generally observed that the portions of the system that cover lit
>>>> (which includes FileCheck) aren't very well behaved.
>>> 
>>> I've filed https://bugs.llvm.org/show_bug.cgi?id=42921 upstream,
>>> hopefully someone who understand this part of the cmake system will help
>>> us out.
>> 
>> You mentioned applying the patch but not also
>> setting:
>> 
>> LLVM_ENABLE_Z3_SOLVER:BOOL=OFF
>> 
>> with either:
>> 
>> -D LLVM_ENABLE_Z3_SOLVER:BOOL=OFF
>> 
>> on the command line or some line early in CMakeCache.txt .
>> (Actually, I had to look around to know to say those
>> specifics of what it means to have already initialized
>> LLVM_ENABLE_Z3_SOLVER .)
>> 
>> From what I see, taking the initial assignment via CMakeCache.txt
>> after it is initialized seems to be a common technique of controlling
>> the configuration.
>> 
>> Taking from an example from web of a CMakeCache.txt . . .
>> 
>> 
>> # This is the CMakeCache file.
>> # For build in directory: [edited out]
>> # It was generated by CMake: /Applications/CMake.app/Contents/bin/cmake
>> # You can edit this file to change values found and used by cmake.
>> # If you do not want to change any of the values, simply exit the editor.
>> # If you do want to change a value, simply edit, save, and exit the editor.
>> # The syntax for the file is as follows:
>> # KEY:TYPE=VALUE
>> # KEY is the name of a variable in the cache.
>> # TYPE is a hint to GUIs for the type of VALUE, DO NOT EDIT TYPE!.
>> # VALUE is the current value for the KEY.
>> 
>> ########################
>> # EXTERNAL cache entries
>> ########################
>> 
>> //Build a 32 bit version of the library.
>> BENCHMARK_BUILD_32_BITS:BOOL=OFF
>> 
>> . . . (lots omitted) . . .
>> 
>> 
>> //Fail and stop if a warning is triggered.
>> LLVM_ENABLE_WERROR:BOOL=OFF
>> 
>> //Enable Support for the Z3 constraint solver in LLVM.
>> LLVM_ENABLE_Z3_SOLVER:BOOL=OFF
>> 
>> //Use zlib for compression/decompression if available.
>> LLVM_ENABLE_ZLIB:BOOL=ON
>> 
>> . . . (lots more omitted) . . .
>> 
>> 
>> The example already had the "LLVM_ENABLE_Z3_SOLVER:BOOL=OFF"
>> line, I did not adjust it.
> 
> Upstream spotted this error as well.  I've hopefully committed a fix (of
> course just as I committed I discovered I'd had the patch applied and it
> shouldn't be needed so I'm now rebuilding again and will add the patch
> if needed.)

Just for my curiosity: which way are you
initializing LLVM_ENABLE_Z3_SOLVER to OFF ?:

A) Having -D LLVM_ENABLE_Z3_SOLVER:BOOL=OFF on the cmake command line?
B) Having LLVM_ENABLE_Z3_SOLVER:BOOL=OFF in the CMakeCache.txt file?
C) Something else (that I missed as a technique)?


===
Mark Millard
marklmi at yahoo.com
( dsl-only.net went
away in early 2018-Mar)

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