Compiler bug workaround for using format() in a user-defined module
#4919
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
Verified that without the product code workaround, this fails with: D:\GitHub\STL\out\x64\out\inc\format(2635): error C3688: invalid literal suffix 'sv'; literal operator or literal operator template 'operator ""sv' not found D:\GitHub\STL\out\x64\out\inc\format(2637): error C3688: invalid literal suffix 'sv'; literal operator or literal operator template 'operator ""sv' not found D:\GitHub\STL\out\x64\out\inc\format(2639): error C3688: invalid literal suffix 'sv'; literal operator or literal operator template 'operator ""sv' not found D:\GitHub\STL\out\x64\out\inc\format(2641): error C3688: invalid literal suffix 'sv'; literal operator or literal operator template 'operator ""sv' not found D:\GitHub\STL\out\x64\out\inc\format(2644): error C3688: invalid literal suffix 'sv'; literal operator or literal operator template 'operator ""sv' not found Perl also tested positively and negatively.
StephanTLavavej
added
bug
CaseyCarter
approved these changes
Aug 27, 2024
|
I'm mirroring this to the MSVC-internal repo - please notify me if any further changes are pushed. |
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Outdated suggestions cannot be applied.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.
DevCom-10313766 VSO-1775715 "Using
std::formatin a module requires including<format>header in .cpp files using that module" is caused by a compiler bug where the compiler is currently unable to encode UDLs in the IFC. The workaround is to avoid UDLs. Constructing temporaries of length 2 or 1 was the simplest, compared to extracting namedconstexprvariables.Since the workaround is relatively simple but affects several lines, I chose to make it unconditional (instead of guarding it for MSVC only), and I commented only the first occurrence (no reason to repeat it on every line). My hope is that the compiler will be fixed very soon (@cdacamar is investigating).
I audited the STL for other UDLs in our headers, and
<filesystem>was the only other user of UDLs. However, all of its usage was in non-templated functions, which appear to be immune to the compiler bug, so I don't believe that<filesystem>changes are necessary.This scenario, where the STL is included in the Global Module Fragment of a user-defined module, is clearly under-explored - along the way I encountered and reported the much more severe VSO-2227713 "Modules: Exported function templates can't use
std::coutproperly" (with no known workaround). So, I'm adding a dedicated test for this scenario, currently just exercising theformat()scenario but available to extend in the future. I had to extractP2465R3_standard_library_modules/env.lst(because we have to handle the usually-force-included machinery specially, and can't tolerate/permissive, we need dedicated configurations).This requires special Python and Perl machinery to compile the
user.ixxbefore thetest.cpp, but very similar to existing tests that we have elsewhere. I verified both the GitHub Python and internal Perl test harnesses, both positively (test passes with product changes) and negatively (test fails without product changes).