Avoid ODR violations with flatbuffers::Verifier. #8274
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
Fix "One Definition Rule" violation when using flatbuffers::Verifier with FLATBUFFERS_TRACK_VERIFIER_BUFFER_SIZE defined in some compilation units and not defined in other compilation units. The fix is to make Verifier a template class, with a boolean template parameter replacing the "#ifdef" conditionals; to rename it as VerifierTemplate; and then to use "#ifdef" only for a "using" declaration that defines the original name Verifier an an alias for the instantiated template. In this way, even if FLATBUFFERS_TRACK_VERIFIER_BUFFER_SIZE is defined in some compilation units and not in others, as long as clients only reference flatbuffers::Verifier in .cc files, not header files, there will be no ODR violation, since the only part whose definition varies is the "using" declaration, which does not have external linkage. There is still some possibility of clients creating ODR violations if the client header files (rather than .cc files) reference flatbuffers::Verifier. To avoid that, this change also deprecates FLATBUFFERS_TRACK_VERIFIER_BUFFER_SIZE, and instead introduces flatbuffers::SizeVerifier as a public name for the template instance with the boolean parameter set to true, so that clients don't need to define the macro at all.
dbaileychess
approved these changes
Apr 2, 2024
jochenparm
pushed a commit
to jochenparm/flatbuffers
that referenced
this pull request
Oct 29, 2024
Fix "One Definition Rule" violation when using flatbuffers::Verifier with FLATBUFFERS_TRACK_VERIFIER_BUFFER_SIZE defined in some compilation units and not defined in other compilation units. The fix is to make Verifier a template class, with a boolean template parameter replacing the "#ifdef" conditionals; to rename it as VerifierTemplate; and then to use "#ifdef" only for a "using" declaration that defines the original name Verifier an an alias for the instantiated template. In this way, even if FLATBUFFERS_TRACK_VERIFIER_BUFFER_SIZE is defined in some compilation units and not in others, as long as clients only reference flatbuffers::Verifier in .cc files, not header files, there will be no ODR violation, since the only part whose definition varies is the "using" declaration, which does not have external linkage. There is still some possibility of clients creating ODR violations if the client header files (rather than .cc files) reference flatbuffers::Verifier. To avoid that, this change also deprecates FLATBUFFERS_TRACK_VERIFIER_BUFFER_SIZE, and instead introduces flatbuffers::SizeVerifier as a public name for the template instance with the boolean parameter set to true, so that clients don't need to define the macro at all.
jochenparm
pushed a commit
to jochenparm/flatbuffers
that referenced
this pull request
Oct 29, 2024
Fix "One Definition Rule" violation when using flatbuffers::Verifier with FLATBUFFERS_TRACK_VERIFIER_BUFFER_SIZE defined in some compilation units and not defined in other compilation units. The fix is to make Verifier a template class, with a boolean template parameter replacing the "#ifdef" conditionals; to rename it as VerifierTemplate; and then to use "#ifdef" only for a "using" declaration that defines the original name Verifier an an alias for the instantiated template. In this way, even if FLATBUFFERS_TRACK_VERIFIER_BUFFER_SIZE is defined in some compilation units and not in others, as long as clients only reference flatbuffers::Verifier in .cc files, not header files, there will be no ODR violation, since the only part whose definition varies is the "using" declaration, which does not have external linkage. There is still some possibility of clients creating ODR violations if the client header files (rather than .cc files) reference flatbuffers::Verifier. To avoid that, this change also deprecates FLATBUFFERS_TRACK_VERIFIER_BUFFER_SIZE, and instead introduces flatbuffers::SizeVerifier as a public name for the template instance with the boolean parameter set to true, so that clients don't need to define the macro at all.
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.
Fix "One Definition Rule" violation when using flatbuffers::Verifier with FLATBUFFERS_TRACK_VERIFIER_BUFFER_SIZE defined in some compilation units and not defined in other compilation units.
The fix is to make Verifier a template class, with a boolean template parameter replacing the "#ifdef" conditionals; to rename it as VerifierTemplate; and then to use "#ifdef" only for a "using" declaration that defines the original name Verifier an an alias for the instantiated template. In this way, even if FLATBUFFERS_TRACK_VERIFIER_BUFFER_SIZE is defined in some compilation units and not in others, as long as clients only reference flatbuffers::Verifier in .cc files, not header files, there will be no ODR violation, since the only part whose definition varies is the "using" declaration, which does not have external linkage.
There is still some possibility of clients creating ODR violations if the client header files (rather than .cc files) reference flatbuffers::Verifier. To avoid that, this change also deprecates FLATBUFFERS_TRACK_VERIFIER_BUFFER_SIZE, and instead introduces flatbuffers::SizeVerifier as a public name for the template instance with the boolean parameter set to true, so that clients don't need to define the macro at all.