alt Hacker News> This blog post talks as if mocking the `open` function is a good thing that people should be told how to do. If you are mocking anything in the standard library your code is probably structured poorly.
Valgrind is a mock of standard library/OS functions and I think its existence is a good thing. Simulating OOM is also only possible by mocking stuff like open.
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vkou • yesterday at 10:50 AM
All rules exist to be broken in the right circumstances. But in 99.9% of test code, there's no reason to do any of that.
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> Valgrind is a mock of standard library/OS functions and I think its existence is a good thing.
That is mostly wrong.
Valgrind wraps syscalls. For the most part it just checks the arguments and records any reads or writes to memory. For a small number of syscalls it replaces the syscall rather than wrapping it (for instance calls like getcontext where it needs to get the context from the VEX synthetic CPU rather than the real CPU).
Depending on the tool it can also wrap or replace libc and libpthread functions. memcheck will replace all allocation functions. DRD and Helgrind wrap all pthread functions.