fingolfin
commented
7 years ago We have to essentially cater for two kinds of packages: Those using autoconf and m4/ac_find_gap.m4; and those using gac. For the latter, things are actually easier because gac is a shell script and we can modify it to do our bidding.
So I'll focus on those using m4/ac_find_gap.m4. There are two setups to support:
A. The easy one is to support in-tree builds of GAP, i.e. where you simply run ./configure && make within the GAP source tree.
B. The harder one is to support out-of-tree builds.
Let's consider case A first. Here is what AC_FIND_GAP does and how to deal with it:
- It looks for
$GAPROOT/sysinfo.gap, which we therefore should add. - It parses that file, and then looks for two more files:
$GAPROOT/src/compiled.hand$GAPROOT/bin/$GAPARCH/config.h. The former is of course fine. To make the latter work, we could setGAPARCHto../src; but it's probably better to set it to some fake value, and then symlinkconfig.h. - It looks for
$GAPROOT/bin/$GAPARCH/extern/gmp/include/gmp.hto see if a bundled GMP was compiled; if so, it adds$GAPROOT/bin/$GAPARCH/extern/gmp/includeto the list of include paths. To resolve this, add a suitable symlink. - It sets
GAP_CPPFLAGS="-I$GAPROOT -I$GAPROOT/bin/$GAPARCH". Nothing needs to be done.
Now let's consider case B. This is a bit more complicated. Suppose the GAP source tree is in REAL_GAPROOT, but we chose to run configure out of tree, in directory GAPROOT. We then later point the package's configure script at GAPROOT. We need to deal with the same four points:
$GAPROOT/sysinfo.gapis again no problem (indeed, we can just letconfigurecreate it for us fromsysinfo.gap.in, and it will automatically end up in the right place- Ensuring that
config.his found is again trivial. But now we also need to worry aboutsrc/compiled.h. Let's postpone that for the moment - Finding GMP: same as above
- To get the include flags right, we could try to set
GAPARCHto a "crazy" value so that$GAPROOT/bin/$GAPARCHends up pointing atREAL_GAPROOT. But some packages will useGAPARCHfor other things. So again it's better to work with a symlink.
So for steps 2 and 4, we need to ensure that the GAP header files from REAL_GAPROOT/src/*.h can also be found under GAPROOT/src/. We can solve this in multiple ways, with different pros and cons:
i. Symlink the directory REAL_GAPROOT/src to GAPROOT/src. But we currently output config.h and .o files into GAPROOT/src. Solution: Output the .o files to e.g. GAPROOT/obj and config.h to e.g. just GAPROOT (but then we need to adjust how we include it). Another drawback of this method: I am not sure it'll work on Windows. ii. Symlink the filesREAL_GAPROOT/src/.hintoGAPROOT/src(and the same forsrc/hpc/.h`). But be careful to add/remove symlinks whenever header files are added/removed. And again, Windows support might be a problem.
iii. The same as in the previous approach, but copy (and delete) headers as appropriate. This would certainly work on Windows. However, this is very error prone and requires utmost care, lest a developer edits a file in the wrong place.
I kind of prefer approach i., as it seems to require the least work and attention to minute detail.
olexandr-konovalov
From TODO file: add fake GAP arch for compatibility mode