[package] boost/1.74.0: won't link

[bahlborn]

Package and Environment Details (include every applicable attribute)

• Package Name/Version: boost/1.74.0
• Operating System+version: Windows 10 Pro 10.0.19042 Build 19042
• Compiler+version: MSVC 2019 version 16.9.1
• Conan version: conan 1.35.0
• Python version: Python 3.9.1

Conan profile (output of conan profile show default or conan profile show <profile> if custom profile is in use)

[settings]
os=Windows
os_build=Windows
arch=x86_64
arch_build=x86_64
build_type=Release
[options]
[build_requires]
[env]

Steps to reproduce (Include if Applicable)

Using cmake_find_package generator and cmake find_package(Boost), the following error happens when linking:
LNK1104 cannot open file 'libboost_filesystem-vc142-mt-sgd-x64-1_74.lib'

[Nekto89]

Are you using "Boost::disable_autolinking"?

[bahlborn]

I don’t believe so. I am double checking with another member of the team who setup the project. An additional piece of information; in the project where the link error occurred, we were linking Boost::headers. Changing this to Boost::Boost allows the project to link. From: Marian Klymov ***@***.***> Sent: Thursday, April 8, 2021 8:32 AM To: conan-io/conan-center-index ***@***.***> Cc: Ben Ahlborn ***@***.***>; Author ***@***.***> Subject: Re: [conan-io/conan-center-index] [package] boost/1.74.0: won't link (#5156) Are you using "Boost::disable_autolinking"? — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub<#5156 (comment)>, or unsubscribe<https://github.com/notifications/unsubscribe-auth/ATS3FJUKMOIZOWR3UHYGWOTTHXD7FANCNFSM42S7FGXA>.

[bahlborn]

We are not explicitly setting it, but we do see a message in the output message “boost/1.74.0: Disabled magic autolinking (smart and magic decisions)”. From: Marian Klymov ***@***.***> Sent: Thursday, April 8, 2021 8:32 AM To: conan-io/conan-center-index ***@***.***> Cc: Ben Ahlborn ***@***.***>; Author ***@***.***> Subject: Re: [conan-io/conan-center-index] [package] boost/1.74.0: won't link (#5156) Are you using "Boost::disable_autolinking"? — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub<#5156 (comment)>, or unsubscribe<https://github.com/notifications/unsubscribe-auth/ATS3FJUKMOIZOWR3UHYGWOTTHXD7FANCNFSM42S7FGXA>.

[helmesjo]

@Nekto89 Any ideas for this? Basically when "linking" the headers-only target Boost::headers it appears to still include actual targets to link (and the wrong lib-names: libboost_filesystem-vc142-mt-sgd-x64-1_74.lib instead of the correct libboost_filesystem.lib), not only headers/include paths.
@madebr Since you did #2097 (which worked in this case when it was first merged), do you spot any oddities in recent changes? Since one doesn't necessarily clear the cache every day it's hard to tell when this started happening (and what commit that's possibly the culprit).

[madebr]

@helmesjo

The "Disabled magic autolinking (smart and magic decisions)" message is emitted here:

conan-center-index/recipes/boost/all/conanfile.py

Lines 1218 to 1228 in f423487

	if self._is_msvc or self._is_clang_cl:
	if self.options.magic_autolink:
	if self.options.layout == "system":
	self.cpp_info.components["_libboost"].defines.append("BOOST_AUTO_LINK_SYSTEM")
	elif self.options.layout == "tagged":
	self.cpp_info.components["_libboost"].defines.append("BOOST_AUTO_LINK_TAGGED")
	self.output.info("Enabled magic autolinking (smart and magic decisions)")
	else:
	# DISABLES AUTO LINKING! NO SMART AND MAGIC DECISIONS THANKS!
	self.cpp_info.components["disable_autolinking"].defines = ["BOOST_ALL_NO_LIB"]
	self.output.info("Disabled magic autolinking (smart and magic decisions)")

Try adding add_definitions(BOOST_ALL_NO_LIB) to the top of your cmake build script (after project).
It that works, then somehow the incorrect compile flags are passed to the compiler.

See https://www.boost.org/doc/libs/1_75_0/libs/config/doc/html/index.html#boost_config.configuring_boost_for_your_platform.user_settable_options for the available definitions.

[helmesjo]

@madebr With add_definitions(-DBOOST_ALL_NO_LIB) it doesn't fail on the missing lib so I guess your hypothesis is correct.
But now instead I get unresolved symbols pointing to boost::filesystem so it appears some header we use is still calling functions from that lib.

[madebr]

All cmake targets that use boost's filesystem or are exposing boost filesystem through its headers must link to Boost::filesystem.
See https://cmake.org/cmake/help/latest/module/FindBoost.html#imported-targets for the available targets.

[helmesjo]

Thanks! Yeah, had to dig through the includes in boost/process to see that it reaches into filesystem (even though the error already suggested this), but it was hard to figure this one out since the documentation doesn't appear to explicitly say it (or I'm just poor at googling).

So basically Boost::process is a header-only lib that requires other non-header-only libs..? Linking Boost::headers & Boost::filesystem appears to be enough.

Now there is just the problem that linking only Boost::headers tricks CMake into automagically link non-existing libraries (wrong naming convention) I guess (but yes I can get around that for now by explicitly linking both headers & filesystem).

[madebr]

The current conanfile only passes these definitions (BOOST_ALL_NO_LIB) for the library components, not for the header component.
Maybe we should change this to add these defines to the header component.

Soon, boost 1.75.0 will be released.
I'll try to shove in this change.

[madebr]

I am now going through the boost recipe to add 1.76.0.
I will not make the change I suggested in my previous comment
The FindBoost document suggests to use Boost::disable_autolinking to "disable automatic linking with MSVC (adds -DBOOST_ALL_NO_LIB)".

[SSE4]

need to link with Boost::disable_autolinking in order to disable auto-linking