fafbf8acf4 Make G_FUZZING constexpr, require -DBUILD_FOR_FUZZING=ON to execute a fuzz target (MarcoFalke)
fae3cf0ffa ci: Temporarily disable macOS/Windows fuzz step (MarcoFalke)
Pull request description:
`g_fuzzing` is used inside `Assume` at runtime, causing significant overhead in hot paths. See https://github.com/bitcoin/bitcoin/issues/31178
One could simply remove the `g_fuzzing` check from the `Assume`, but this would make fuzzing a bit less useful. Also, it would be unclear if `g_fuzzing` adds a runtime overhead in other code paths today or in the future.
Fix all issues by making `G_FUZZING` equal to the build option `BUILD_FOR_FUZZING`, and for consistency in fuzzing, require it to be set when executing any fuzz target.
Fixes https://github.com/bitcoin/bitcoin/issues/31178
Temporarily this drops fuzzing from two CI tasks, but they can be re-added in a follow-up with something like https://github.com/bitcoin/bitcoin/pull/31073
ACKs for top commit:
marcofleon:
Tested ACK fafbf8acf4
davidgumberg:
I still ACK fafbf8acf4 for fixing the regression measured in #31178.
ryanofsky:
Code review ACK fafbf8acf4 but approach -0, because this approach means libraries built for fuzz testing do not function correctly if used in a release, and libraries built for releases are mostly useless for fuzz testing. So I would like to at least consider other solutions to this problem even if we go with this one.
dergoegge:
utACK fafbf8acf4
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