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Malloc thread-safe?
I heard that glibc malloc() was not thread safe, since several threads of a process calling malloc() simultaneously will lead to undefined behaviour. And my question is if a thread calls free() will another thread is calling malloc(), will this lead to undefined behaviour as well?
If you link with -pthreads, malloc() will be threadsafe in glibc.
Without that, the linker doesn't link in a threadsafe malloc, which will lead to undefined behavior.
It depends upon your glibc implementation. A simple "man malloc" on your system might tell you. In general if you tell the compiler that you will be using threads then it will link in a thread safe version of the c runtime library including a thread-safe malloc().
It really depends on the memory allocator you're using, however, I think by default, malloc and free are non-reentrant as they maintain the list of blocks of memory in a static list.
This could lead to complications if you're malloc'ing and freeing simultaneously.
I know that ptmalloc, however, is threadsafe, so you could use that instead.
These links were also useful:
