Fix unused return value warnings which manifest as errors. #1396
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This should be the correct fix for the build issues that came up on recent ECH changes. Background: Unless you install Clang and take steps to make it the default compiler, then on many Linux distributions (esp Ubuntu) the JNI code will get built with gcc. gcc does not consider casting to void is sufficient to avoid a warning about unused returns from a function which has the warn_unused_result attribute. This change assigns the result to a variable with the CONSCRYPT_UNUSED attribute which works correctly on Clang, gcc and MSVC. As for why it's OK in these cases: The asprintf methods should probably *not* ignore the value but they're calling FatalError with the result so it's game over anyway. This method could use re-writing but not this PR. The read and write on fdsEmergency in native_crypto is part of an "interesting" mechanism to prevent blocking forever when using the ConscryptFileDescriptorSocket implementation, which ought to go away but works as-is.
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Historic discussion about gcc's behaviour: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66425 😄 |
tweksteen
approved these changes
Oct 8, 2025
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This should be the correct fix for the build issues that came up on recent ECH changes.
Background: Unless you install Clang and take steps to make it the default compiler, then on many Linux distributions (esp Ubuntu) the JNI code will get built with gcc.
gcc does not consider casting to void is sufficient to avoid a warning about unused returns from a function which has the warn_unused_result attribute.
This change assigns the result to a variable with the CONSCRYPT_UNUSED attribute which works correctly on Clang, gcc and MSVC.
As for why it's OK in these cases:
The asprintf methods should probably not ignore the value but they're calling FatalError with the result so it's game over anyway. This method could use re-writing but not this PR.
The read and write on fdsEmergency in native_crypto is part of an "interesting" mechanism to prevent blocking forever when using the ConscryptFileDescriptorSocket implementation, which ought to go away but works as-is.