It's highly unlikely that the maintainer of OpenSSL at Debian is a spec lawyer. The maintainer ran Valgrind because, as a general principle, reading undefined memory is bad. That is independent of whether the C standard says that it's OK. If I were the maintainer of the package in question, I would not ignore reads of undefined memory just because the C committee has declared that it has some kind of behavior. That would be silly.
Valgrind contains many tools that check for things that are not violations of the C standard: for example, memcheck checks for "fishy" arguments to malloc that are not C standard violations but are nevertheless usually bugs.
> Compilers may not turn functions that hit most kinds of UB into { return; }, but they can. As a general category, that's a bad thing.
Depends on the undefined behavior. For undefined behavior coming from the C preprocessor, sure, that shouldn't be undefined, and the committee should change the spec. For other kinds of UB, if compiler authors hadn't figured out those tricks, we'd have slower programs today. Undefined behavior is much of what has allowed performance of our programs to keep improving despite the language not changing over decades.
I don't blame all problems on C, but I think it should be easier to write valid C. Dealing with uninitialized variables was just an example of something that could be changed. It wasn't supposed to be the biggest most horrible problem with C.
Compilers may not turn functions that hit most kinds of UB into { return; }, but they can. As a general category, that's a bad thing.