Please add a cmake variable to use externally installed flint

[yurivict]

flint is packaged on most systems, see https://repology.org/projects/?search=flint

[mahrud]

@DanGrayson the CMake side of this is done. The only exception being when we build with mpir, which requires compiling Flint in order to avoid linking conflicts. So I believe this is a duplicate of #1242.

@yurivict if you'd like to use gmp rather than mpir, and use the system Flint if it has version at least 2.6, add -DWITH_MPIR=OFF to the arguments of CMake.

[DanGrayson]

There seems to be no autotools side of this, since the title refers to cmake, so closing.

[yurivict]

FYI: mpir is also available in ports.

[yurivict]

if you'd like to use gmp rather than mpir, and use the system Flint if it has version at least 2.6, add -DWITH_MPIR=OFF to the arguments of CMake.

This didn't work. It still tries to use the bundled flint project, despite flint2-2.6.0 being present.

-- Found LibXml2: /usr/local/lib/libxml2.so (found suitable version "2.9.10", minimum required is "2.9") 
--  Checking library compatibility
--  Checking library compatibility -  Libraries are compatible!
CMake Error at /usr/local/share/cmake/Modules/ExternalProject.cmake:2659 (message):
  No download info given for 'build-flint' and its source directory:

   /usr/ports/math/macaulay2/work/M2-version-1.15.1.0-460-g6da6a66ec/M2/submodules/flint2

  is not an existing non-empty directory.  Please specify one of:

[DanGrayson]

@DanGrayson the CMake side of this is done. The only exception being when we build with mpir, which requires compiling Flint in order to avoid linking conflicts.

I'd still like to understand how there can be linking conflicts.

[mahrud]

FYI: mpir is also available in ports.

If everything linked with gmp, we could use the system gmp and flint. But an issue occurs when flint is linked with gmp while factory is linked with flint and mpir and M2-binary is linked with flint, factory, and mpir. At best, this produces conflict errors during linking, but at worst it goes unnoticed until freaky bugs present. Here's my thought process on the way the CMake build handles this:

First, if we want to use mpir but the installed flint is linked with gmp, we need to compile flint to avoid link conflicts.

Now that we want to compile flint, we should be careful about the compile flags we give it. On my system (Fedora 32) the installed mpir is mixed with gmp in /usr/lib:

Because of this, we can't just tell flint to compile with -I/usr/include -L/usr/lib, because then it would link with the real gmp in /usr/lib (even if we use the gmp-to-mpir header trick, the library that flint looks for is libgmp).

Instead, CMake defaults to also compiling mpir in usr-host so we can tell flint to compile with -I usr-host/include -L usr-host/lib, so that it finds the "fake gmp" that mpir installs there.

Does this make sense? I don't know of a way to avoid a conflict in this case if we don't compile both flint and mpir. If you know a way, I'd be happy to simplify the build!

[DanGrayson]

If everything linked with gmp, we could use the system gmp and flint. But an issue occurs when flint is linked with gmp while factory is linked with flint and mpir and M2-binary is linked with flint, factory, and mpir. At best, this produces conflict errors during linking, but at worst it goes unnoticed until freaky bugs present.

This is the part I don't understand. I'll do some experiments ...

[yurivict]

There should be a workaround for this. I would like to at least be able to build it, and only using the external gmp and flint and not mpir would be fine.

Rebuilding all dependencies isn't an option due to the need to patch dependencies which is highly undesirable (copying patches from the port to dependent project bundling the same package). Another reason is everything can't be bundled into everything.

[mahrud]

There should be a workaround for this. I would like to at least be able to build it, and only using the external gmp and flint and not mpir would be fine.

Ah, that's my bad ... the correct option is -DUSING_MPIR=OFF (it is mentioned correctly in INSTALL-CMake.md)! Try that instead!

[yurivict]

With -DUSING_MPIR=OFF it fails the same way:

  No download info given for 'build-flint' and its source directory:

   /usr/ports/math/macaulay2/work/M2-version-1.15.1.0-460-g6da6a66ec/M2/submodules/flint2

[mahrud]

Could you send the full output of CMake, perhaps in a gist?