cmake: handle builds that use static toolchain libs #1256
Merged
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
The problem being solved here is: if a toolchain wants to link the toolchain libs statically, there are some flags that need to be passed. Unfortunately, static linking is notoriously order-sensitive (if an object needs a symbol, it can only be resolved by libraries _later_ than it on the command line). This means there are scenarios where: this works: gcc thing.o -o stuff -l:libstdc++.a this fails with missing symbols (like std::cout): gcc -l:libstdc++.a -o stuff thing.o In other words, we need these flags to be in "<LINK_LIBRARIES>" and not just "<LINK_FLAGS>", so they fall after the "<OBJECTS>" that might need them and that is what this code does, by injecting these indicative flags into CMAKE_CXX_STANDARD_LIBRARIES_INIT
novas0x2a
force-pushed
the
cmake-static
branch
from
ef95a65 to
a0013cc
Compare
jsharpe
approved these changes
Aug 12, 2024
jsharpe
pushed a commit
to jsharpe/rules_foreign_cc
that referenced
this pull request
Aug 23, 2024
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
The problem being solved here is: if a toolchain wants to link the toolchain libs statically, there are some flags that need to be passed. Unfortunately, static linking is notoriously order-sensitive (if an object needs a symbol, it can only be resolved by libraries later than it on the command line). This means there are scenarios where
this works:
gcc thing.o -o stuff -l:libstdc++.a
this fails with missing symbols (like std::cout):
gcc -l:libstdc++.a -o stuff thing.o
In other words, we need these flags to be in
<LINK_LIBRARIES>and not just<LINK_FLAGS>, so they fall after the<OBJECTS>that might need them and that is what this code does, by injecting these indicative flags into CMAKE_CXX_STANDARD_LIBRARIES_INITThis is a kind of hacky way to handle this; I suspect once bazelbuild/bazel#23204 lands, it will be possible to do this better.