Bug 927157

Summary:	cmake.eclass: pass -DCMAKE_INTERPROCEDURAL_OPTIMIZATION=OFF
Product:	Gentoo Linux	Reporter:	Sam James <sam>
Component:	Eclasses	Assignee:	Gentoo's Team for Core System packages <base-system>
Status:	CONFIRMED ---
Severity:	normal	CC:	eschwartz93, kde
Priority:	Normal
Version:	unspecified
Hardware:	All
OS:	Linux
See Also:	https://bugs.gentoo.org/show_bug.cgi?id=856778 https://bugs.gentoo.org/show_bug.cgi?id=927037
Whiteboard:
Package list:		Runtime testing required:	---

Description Sam James archtester

2024-03-17 06:13:38 UTC

This came up in bug 856778 where it appears that LTO is coming from pybind11 (!) which defaults to LTO per https://github.com/pybind/pybind11/blob/8b48ff878c168b51fe5ef7b8c728815b9e1a9857/docs/compiling.rst#pybind11_add_module.

We should set -DCMAKE_INTERPROCEDURAL_OPTIMIZATION=OFF in the eclass. THe user can enable LTO if they want.

Alternatively, we could do the meson.eclass appraoch and check for tc-is-lto first...?

Comment 1 Sam James archtester

2024-03-17 06:13:58 UTC

https://cmake.org/cmake/help/latest/prop_tgt/INTERPROCEDURAL_OPTIMIZATION.html#prop_tgt:INTERPROCEDURAL_OPTIMIZATION

https://cmake.org/cmake/help/latest/variable/CMAKE_INTERPROCEDURAL_OPTIMIZATION.html#variable:CMAKE_INTERPROCEDURAL_OPTIMIZATION

Comment 2 Eli Schwartz 2024-03-17 06:30:17 UTC

Note the meson.eclass approach is beneficial since there are meson projects that specifically set some targets known to not work with LTO to off.

e.g. scipy has some really old fortran code with no intention of fixing it, since they just want to migrate *away* from it. So they force LTO off, but other scipy extension modules are expected to work fine.

Similar logic may or may not apply to cmake / projects using cmake. (Or might not apply.)

Comment 3 Mike Gilbert gentoo-dev

2024-03-17 13:27:23 UTC

Note that cmake seems to add -flo=auto when this option is enabled. Not sure if there is any way to control the exact flags it adds.