01960c53c7 fuzz: make FuzzedDataProvider usage deterministic (Martin Leitner-Ankerl)
Pull request description:
There exist many usages of `fuzzed_data_provider` where it is evaluated directly in the function call.
Unfortunately, [the order of evaluation of function arguments is unspecified](https://en.cppreference.com/w/cpp/language/eval_order), and a simple example shows that it can differ e.g. between clang++ and g++: https://godbolt.org/z/jooMezWWY
When the evaluation order is not consistent, the same fuzzing/random input will produce different output, which is bad for coverage/reproducibility. This PR fixes all these cases I have found where unspecified evaluation order could be a problem.
Finding these has been manual work; I grepped the sourcecode for these patterns, and looked at each usage individually. So there is a chance I missed some.
* `fuzzed_data_provider`
* `.Consume`
* `>Consume`
* `.rand`
I first discovered this in https://github.com/bitcoin/bitcoin/pull/29013#discussion_r1420236394. Note that there is a possibility that due to this fix the evaluation order is now different in many cases than when the fuzzing corpus has been created. If that is the case, the fuzzing corpus will have worse coverage than before.
Update: In list-initialization the order of evaluation is well defined, so e.g. usages in `initializer_list` or constructors that use `{...}` is ok.
ACKs for top commit:
achow101:
ACK 01960c53c7
vasild:
ACK 01960c53c7
ismaelsadeeq:
ACK 01960c53c7
Tree-SHA512: e56d087f6f4bf79c90b972a5f0c6908d1784b3cfbb8130b6b450d5ca7d116c5a791df506b869a23bce930b2a6977558e1fb5115bb4e061969cc40f568077a1ad
There exist many usages of `fuzzed_data_provider` where it is evaluated directly in the function call.
Unfortunately, the order of evaluation of function arguments is unspecified. This means it can differ
between compilers/version/optimization levels etc. But when the evaluation order changes, the same
fuzzing input will produce different output, which is bad for coverage/reproducibility.
This PR fixes all these cases where by moving multiple calls to `fuzzed_data_provider` out of the
function arguments.
