base: add a default +debug and +no_opt variant

[seanfarley (Sean Farley)]

This patch adds a default +debug variant that will build packages with -g and, more importantly, run the dsymutil tool to keep the debugging symbols. Additionally, there is a +no_opt variant that will try to delete all -O{1,2,3} flags and add -O0. Of course, individual packages can override what +debug and +no_opt will do, but as a base default, this seems sensible to have so that a user can get debugging symbols for gdb easily without having to edit a package's Portfile.

[ryandesign (Ryan Carsten Schmidt)]

I'm not certain if we want this.

Certainly, we don't want variants whose names begin with "no_" anymore. But on the other hand we don't want to add a default "opt" variant to all ports either; we'd have to rebuild all our binary packages. Could disabling optimizations simply be part of the debug variant?

Why would a normal user want a debug variant? Granted we have it in the cmake portgroup but I'm not sure why we have that either.

[seanfarley (Sean Farley)]

Replying to ryandesign@…:

I'm not certain if we want this.

Certainly, we don't want variants whose names begin with "no_" anymore. But on the other hand we don't want to add a default "opt" variant to all ports either; we'd have to rebuild all our binary packages. Could disabling optimizations simply be part of the debug variant?

Why would a normal user want a debug variant? Granted we have it in the cmake portgroup but I'm not sure why we have that either.

First, having a debug variant is vitally important for macport users, particularly those that build code on top of certain libraries. Take, for instance, PETSc. PETSc can be built on top of gcc4{4,5,6,7}, metis, parmetis, suitesparse, hypre, superlu, superlu_dist, mpich2 (or openmpi), triangle, tetgen, fftw-3, ml, sundials, mumps (which implies scalapack and blacs), hdf5-18, netcdf, libyaml, and valgrind. Adding a +debug variant to all these ports is ... tedious. But without debug symbols being built (and then stashed into a .dSYM) it would be impossible to use gdb my own code that uses PETSc. More over, I found the +debug particularly useful in building my own gfortran port so that gdb worked as expected.

I agree about the +no_opt variant. I did originally have -O0 logic in the +debug variant but that ran into problems with building mpfr. The issue is multi-faceted, unfortunately, with zero optimization. Depending on the compiler, there are different settings for which optimization to use (if nothing is specified most compilers use -O2). Using anything more than -O0 causes problems with debugging because a lot of variables are optimized out, e.g. using 'print var' in gdb causes a hit-or-miss of "variable is optimized out".

So, clearly, not every port can work with -O0 but then again it is *extremely* useful to have a +debug variant to keep the .dSYM files around. I don't know how to proceed. I'm ok with dropping the +no_opt and making each portfile write its own logic for -O0. Probably something like,

pre-configure {
  if {[variant_isset debug]} {
    configure.cflags-append -O0
    ...
  }
}

As an aside for the naming convention, would "+optimization_debug" (or +debug_opt?) have worked? Also, since this is on the subject of variants, a more dangerous idea I had was based off a suggestion on the list: wanting to compile different ports with the same compiler. For example, having a default +gcc44 ... +gcc47, +clang, +system_gcc, +llvm_gcc, etc. Thoughts? (There would be similar problems as having -O0, i.e. some ports wouldn't be able to handle it or would have a cyclic dependency)

[seanfarley (Sean Farley)]

I've updated the patch with a new variant name (and better find command). Any thoughts on the issue?

[seanfarley (Sean Farley)]

Replying to ryandesign@…:

I'm not certain if we want this.

Certainly, we don't want variants whose names begin with "no_" anymore. But on the other hand we don't want to add a default "opt" variant to all ports either; we'd have to rebuild all our binary packages. Could disabling optimizations simply be part of the debug variant?

Why would a normal user want a debug variant? Granted we have it in the cmake portgroup but I'm not sure why we have that either.

Are there any more comments on this patch?

[nerdling (Jeremy Lavergne)]

Having a debug variant available would be handy for people developing directly against said library. Unfortunately, this isn't the typical user and certainly not a majority—the ability to edit the Portfile to include "-g -O0" in the configure.args should be sufficient, or at least has been for me.

[seanfarley (Sean Farley)]

rename the no_opt variant to debug_opt; also use the find command more efficiently

[seanfarley (Sean Farley)]

Replying to snc@…:

Having a debug variant available would be handy for people developing directly against said library. Unfortunately, this isn't the typical user and certainly not a majority—the ability to edit the Portfile to include "-g -O0" in the configure.args should be sufficient, or at least has been for me.

It's more than just adding "-g -O0", it's also generating the .dSYM libraries (at the very least). It is much easier to tell a user "just copy and paste 'sudo port -v install metis +debug' into your terminal" than to tell them to edit a Portfile. Forget about explaining tcl syntax as well. Editing Portfiles becomes a nightmare of maintenance, especially if you're trying to share them with your co-workers. With the newest version of this patch, I've run into no problems (this includes building gcc46, gcc47 as well as other common ports that usually give me trouble).

[nerdling (Jeremy Lavergne)]

Replying to sean.michael.farley@…:

It is much easier to tell a user "just copy and paste 'sudo port -v install metis +debug' into your terminal" than to tell them to edit a Portfile.

I don't have the experience of a situation where I'd need the user (a non-developer) to actually debug a library from MacPorts on my behalf, so I'm wondering if that's worth the burden that Ryan pointed out in the mailing list: having more variants is going to be relatively messy for MacPorts to support.

I definitely like your patches for what they are, though.

[seanfarley (Sean Farley)]

Replying to snc@…:

I don't have the experience of a situation where I'd need the user (a non-developer) to actually debug a library from MacPorts on my behalf, so I'm wondering if that's worth the burden that Ryan pointed out in the mailing list: having more variants is going to be relatively messy for MacPorts to support.

There are a few instances where this has come up very frequently for me. For one, using a gcc4X compiled binary in gdb leads to extremely messy debugging because the compiler itself needs to keep around its own .dSYM files. Further, it seems a case that is being very overlooked here is writing software dependent on libraries that a person doesn't maintain. PETSc is a good example of this (as I outlined in my previous comment). I've been using +debug for almost two years now and it has been a much more sane environment than before.

I definitely like your patches for what they are, though.

Thanks :-) thought at this point, I'd just be happy with getting the +debug variant accepted.

[nonstop.server@…]

Cc Me!

[seanfarley (Sean Farley)]

combine both variants into +debug

[seanfarley (Sean Farley)]

After talking with a colleague, I was convinced it made more sense to go back to my original plan of having just one +debug variant and dropping the +debug_opt. I've submitted a new patch to reflect this.

[su-v]

Cc Me!

[seanfarley (Sean Farley)]

new patch based off reviews from macports-dev

[seanfarley (Sean Farley)]

add dsym to cmake +debug variant

[eborisch (Eric A. Borisch)]

Cc Me!

[mkae (Marko Käning)]

Cc Me!

[axet (Alexey Kuznetsov)]

Cc Me!

[maehne (Torsten Maehne)]

Cc Me!

[cnehren+macports@…]

What's holding this up?

[cnehren+macports@…]

Cc Me!

[seanfarley (Sean Farley)]

Replying to cnehren+macports@…:

What's holding this up?

Some progress has finally been made on this front in r116291. I will be fixing this portgroup up based on feedback I get so that ports can start using this.

[seanfarley (Sean Farley)]

I'm going to close this ticket now and suggest that the macports-dev mailing list be used to talk about how this port group should be improved.