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gh-90539: doc: Expand on what should not go into CFLAGS, LDFLAGS #92754

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vstinner merged 7 commits into from
Jun 20, 2022
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gh-90539: doc: Expand on what should not go into CFLAGS, LDFLAGS #92754

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Doc/using/configure.rst: Expand on what should not go into CFLAGS, LD…
mkoeppe May 12, 2022
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📜🤖 Added by blurb_it.
blurb-it[bot] May 12, 2022
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Doc/using/configure.rst: Fix rst markup
mkoeppe May 14, 2022
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Doc/using/configure.rst: Fixup: LDFLAGS, not CFLAGS
mkoeppe May 14, 2022
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Doc/using/configure.rst: Break a long sentence
mkoeppe May 17, 2022
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Doc/using/configure.rst: Break another long sentence
mkoeppe May 17, 2022
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Misc/NEWS.d/next/Documentation/2022-05-12-23-47-17.gh-issue-90539.nmR…
mkoeppe Jun 17, 2022
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Doc/using/configure.rst: Break another long sentence 
Co-authored-by: Adam Turner <9087854+AA-Turner@users.noreply.github.com>
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mkoeppe and AA-Turner authored May 17, 2022
commit 04a9c4f782d01c8378a5a155f9b5442807935ec5
4 changes: 2 additions & 2 deletions Doc/using/configure.rst
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Expand Up @@ -872,8 +872,8 @@ Linker flags

In particular, :envvar:`LDFLAGS` should not contain:

* the compiler flag `-L` (for setting the search path for libraries);
the `-L` flags are processed from left to right, and any flags in
* the compiler flag `-L` (for setting the search path for libraries).
The `-L` flags are processed from left to right, and any flags in
:envvar:`LDFLAGS` would take precedence over user- and package-supplied `-L`
flags.
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@native-api native-api Jun 13, 2022 •
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In pyenv/pyenv#2381, we found out that at least one -L flag from LDFLAGS was required when linking against Python to find libintl. We even had to add it to python-config --ldflags via a hack since python-config ignores compile-time LDFLAGS for some reason.

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@mkoeppe mkoeppe Jun 13, 2022

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Do you think we should add guidance here for downstream packagers that informs them of other, more suitable ways to set flags -- namely setting environment variables CFLAGS, LDFLAGS, CPATH, LIBRARY_PATH at the runtime of Python?

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@native-api native-api Jun 13, 2022

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setting environment variables CFLAGS, LDFLAGS, CPATH, LIBRARY_PATH at the runtime of Python?

I'm not sure how you expect downstream packagers to do that -- and why they need to do that in the first place since distutils and python-config specifically exist to take care of providing all the necessary flags to link against a specific Python installation.

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@mkoeppe mkoeppe Jun 13, 2022

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Aren't the pyenv shims already setting environment variables? Specifically, they are setting PATH. https://trac.sagemath.org/ticket/29285#comment:20

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@mkoeppe mkoeppe Jun 13, 2022

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I'm not sure how you expect downstream packagers to do that

conda and nix use activation scripts for their environments. homebrew provides brew sh for this purpose.

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@native-api native-api Jun 17, 2022

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If we set the flags in an envvar, they would likely still override package-supplied flags (skimmed through distutils sources, it looks like that). If so, that won't help your original problem.

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@mkoeppe mkoeppe Jun 17, 2022

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That may be true for CFLAGS, but definitely not for CPATH. By the way, https://github.com/pypa/setuptools/blob/main/docs/userguide/ext_modules.rst now has some info (from my PR pypa/setuptools#3368); we can expand it to cover all necessary details to resolve this discussion.

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@mkoeppe mkoeppe Jun 17, 2022

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This is now pypa/setuptools#3387


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