[bug] Adding mold linker to conanfile causes dependency loop

rdong8 commented 2 days ago

Describe the bug

OS: Fedora 41 Compiler: Clang 19.1.0 Conan version: 2.9.2

How to reproduce it

Add the sections from this page to your conanfile. Then run your conan install, ie.:

BUILD_DIR=build conan install . -b missing -pr:b local -pr:h default -s build_type=Release -s "&:build_type=Debug"     │

Result:

======== Input profiles ========
Profile host:
[settings]
arch=x86_64
build_type=Release
compiler=clang
compiler.cppstd=26
compiler.libcxx=libc++
compiler.version=19
os=Linux
&:build_type=Debug
[platform_tool_requires]
cmake/3.31.0
[conf]
tools.cmake.cmaketoolchain:generator=Ninja Multi-Config
[buildenv]
CC=clang
CXX=clang++

Profile build:
[settings]
arch=x86_64
build_type=Release
compiler=clang
compiler.cppstd=26
compiler.libcxx=libc++
compiler.version=19
os=Linux
[tool_requires]
*: mold/[*]
[conf]
tools.build:exelinkflags=['-fuse-ld=mold']
tools.build:sharedlinkflags=['-fuse-ld=mold']

======== Computing dependency graph ========
Graph root
    conanfile.py: /home/rd8/Projects/cpp_project/conanfile.py
Requirements
    boost/1.86.0#46c984e8737c8b910597294db3838f3b - Cache
    bzip2/1.0.8#d00dac990f08d991998d624be81a9526 - Cache
    libbacktrace/cci.20210118#a7691bfccd8caaf66309df196790a5a1 - Cache
    zlib/1.3.1#f52e03ae3d251dec704634230cd806a2 - Cache
Build requirements
    b2/5.2.1#91bc73931a0acb655947a81569ed8b80 - Cache
    mold/2.34.1#4d062e19dee8474c93eddf2af9ea3dfe - Cache
    zlib/1.3.1#f52e03ae3d251dec704634230cd806a2 - Cache
Resolved version ranges
    b2/[>=5.2 <6]: b2/5.2.1
    mold/[*]: mold/2.34.1
    zlib/[>=1.2.11 <2]: zlib/1.3.1
ERROR: There is a cycle/loop in the graph:
    Initial ancestor: mold/2.34.1
    Require: mold/2.34.1
    Dependency: mold/2.34.1

AbrilRBS commented 2 days ago

Hi @rdong8 thanks a lot for taking the time to report this

This is probably not a bug, but expected behaviour.

Your [tool_requires] section on the build profile reads

[tool_requires]
*: mold/[*]

This means that every package in the build context will have mold injected as an extra tool_require.

As * also matches mold, this means that mold is getting itself injected as a tool_require

2 things to note here:

You probably want this [tool_require] section on your host profile, not necessarily as much in the build one. As it stands right now, none of your actual libraries would be using mold.
IF you also end up needed mold as part of your build context profile, you should specify the pattern as !mold/*: mold/[*] to exclude itself. Note that if mold has dependencies and those get the linker injected, you'll still have loops

Let me know if this helps :)

rdong8 commented 2 days ago

Hey, thanks for the response. I have made the following changes:

build:

[buildenv]
CC=clang
CXX=clang++

[conf]
tools.cmake.cmaketoolchain:generator=Ninja Multi-Config

[platform_tool_requires]
cmake/3.31.0

[settings]
arch=x86_64
build_type=Release
compiler=clang
compiler.cppstd=26
compiler.libcxx=libstdc++11
compiler.version=19
os=Linux

host:

[buildenv]
CC=clang
CXX=clang++

[conf]
tools.build:exelinkflags=['-fuse-ld=mold']
tools.build:sharedlinkflags=['-fuse-ld=mold']

[settings]
arch=x86_64
build_type=Release
compiler=clang
compiler.cppstd=26
compiler.libcxx=libc++
compiler.version=19
os=Linux

[tool_requires]
!mold/*: mold/[*]

However I still do have the issue with the dependency loop:

======== Computing dependency graph ========
Graph root
    conanfile.py: /home/rd8/Projects/cpp_project/conanfile.py
Requirements
    boost/1.86.0#46c984e8737c8b910597294db3838f3b - Cache
    bzip2/1.0.8#d00dac990f08d991998d624be81a9526 - Cache
    catch2/3.7.1#431d772165ed0bc5adaabaa44a9f53ca - Cache
    libbacktrace/cci.20210118#a7691bfccd8caaf66309df196790a5a1 - Cache
    spdlog/1.14.1#4fd40d9cbc1978247443a10d2ace58fd - Cache
    zlib/1.3.1#f52e03ae3d251dec704634230cd806a2 - Cache
Build requirements
    b2/5.2.1#91bc73931a0acb655947a81569ed8b80 - Cache
    cmake/3.31.0 - Platform
    mold/2.34.1#4d062e19dee8474c93eddf2af9ea3dfe - Cache
    xxhash/0.8.2#03fd1c9a839b3f9cdf5ea9742c312187 - Cache
    zlib/1.3.1#f52e03ae3d251dec704634230cd806a2 - Cache
Resolved version ranges
    b2/[>=5.2 <6]: b2/5.2.1
    mold/[*]: mold/2.34.1
    zlib/[>=1.2.11 <2]: zlib/1.3.1

======== Computing necessary packages ========
spdlog/1.14.1: Main binary package '4c4d5237d406fd4c79c7bef05af533c8939e3c58' missing
spdlog/1.14.1: Checking 5 compatible configurations
spdlog/1.14.1: Compatible configurations not found in cache, checking servers
spdlog/1.14.1: '6679d20ab72b8fd423ecd46d0746e46c39770bcf': compiler.cppstd=20
spdlog/1.14.1: '60e040ab069a2b5d5c85ecd731af4cf86f9c230c': compiler.cppstd=gnu20
spdlog/1.14.1: '603d38981bae7e65f2e73ff7f9f51e59a201279e': compiler.cppstd=23
spdlog/1.14.1: '494d27793e5f9f33c2929a3b7c28a43c29aead3f': compiler.cppstd=gnu23
spdlog/1.14.1: '0b9f5ef239a0d52320e31bb08c49326c6a4621c3': compiler.cppstd=gnu26
boost/1.86.0: Main binary package 'c123612e482b0a8ecc61a6ddb0a62d25e7578366' missing
boost/1.86.0: Checking 5 compatible configurations
boost/1.86.0: Compatible configurations not found in cache, checking servers
boost/1.86.0: 'af3e0258503efbefd0af55b4f2db656adc861436': compiler.cppstd=20
boost/1.86.0: '3427da6b3ac26939436d8224d9e5ec48f192a412': compiler.cppstd=gnu20
boost/1.86.0: 'cbf236643def2491b4668a4a48b7a8131c6d5623': compiler.cppstd=23
boost/1.86.0: 'c9e387a2d958cc83509b4521866344929375614a': compiler.cppstd=gnu23
boost/1.86.0: '728d5f8f5ab862ab57258b1bfca76baba484a027': compiler.cppstd=gnu26
Requirements
    boost/1.86.0#46c984e8737c8b910597294db3838f3b:c123612e482b0a8ecc61a6ddb0a62d25e7578366 - Build
    bzip2/1.0.8#d00dac990f08d991998d624be81a9526:ab19b9bfc1b47ea17e1a675221a2f0b1e27ebba5 - Build
    catch2/3.7.1#431d772165ed0bc5adaabaa44a9f53ca:882cd1aca82e6fa218c2563f3d8e8bee421ac4a8 - Build
    libbacktrace/cci.20210118#a7691bfccd8caaf66309df196790a5a1:035983102d94f5d9d7256017a5fd89651d1294c3 - Build
    spdlog/1.14.1#4fd40d9cbc1978247443a10d2ace58fd:4c4d5237d406fd4c79c7bef05af533c8939e3c58 - Build
    zlib/1.3.1#f52e03ae3d251dec704634230cd806a2:035983102d94f5d9d7256017a5fd89651d1294c3 - Build
Build requirements
    b2/5.2.1#91bc73931a0acb655947a81569ed8b80:63fead0844576fc02943e16909f08fcdddd6f44b#f9c46d924270b1920fa5398114be2576 - Download (conancenter)
    cmake/3.31.0 - Platform
    mold/2.34.1#4d062e19dee8474c93eddf2af9ea3dfe:77dc507434abadcc87e1517333a94365a4b99b07 - Build
    xxhash/0.8.2#03fd1c9a839b3f9cdf5ea9742c312187:aa3784fb750b4514cd847a028afd1f7efa4e7711 - Build
    zlib/1.3.1#f52e03ae3d251dec704634230cd806a2:035983102d94f5d9d7256017a5fd89651d1294c3 - Build
ERROR: There is a loop in the graph (some packages already ommitted):
zlib/1.3.1 (Build) -> ['mold/2.34.1']
mold/2.34.1 (Build) -> ['zlib/1.3.1', 'xxhash/0.8.2', 'cmake/3.31.0']
bzip2/1.0.8 (Build) -> ['mold/2.34.1']
catch2/3.7.1 (Build) -> ['mold/2.34.1']
libbacktrace/cci.20210118 (Build) -> ['mold/2.34.1']
spdlog/1.14.1 (Build) -> ['mold/2.34.1']
boost/1.86.0 (Build) -> ['zlib/1.3.1', 'bzip2/1.0.8', 'libbacktrace/cci.20210118', 'b2/5.2.1', 'mold/2.34.1']

This graph is ill-formed, and cannot be installed
Most common cause is having dependencies both in build and host contexts
forming a cycle, due to tool_requires having transitive requires.
Check your profile [tool_requires] and recipe tool and regular requires
You might inspect the dependency graph with:
  $ conan graph info . --format=html > graph.html

Would it help if I installed mold external to conan and somehow just told conan to use that? I'm not sure if I follow fully but it seems like part of the problem is mold itself needing to be built.

conan-io / conan

[bug] Adding mold linker to conanfile causes dependency loop #17333

Describe the bug

How to reproduce it