问题
Why is calling a standard library function inside a signal handler discouraged?
回答1:
This is explained in the GNU LibC documentation.
If you call a function in the handler, make sure it is reentrant with respect to signals, or else make sure that the signal cannot interrupt a call to a related function.
And just in case, here's the Wikipedia page on reentrant functions.
A computer program or routine is described as reentrant if it can be safely called again before its previous invocation has been completed (i.e it can be safely executed concurrently).
回答2:
Its not only re-entrancy issues, depending on the signal being services you also want to avoid inadvertent calls to malloc() (i.e. asprintf()) and other variadic expansion (i.e. printf()).
回答3:
It is all running fine and stuff, until you run into some mysterious bugs which are totally untraceable :)
man 7 signal will give you a list of system calls which are safe to call from a signal handler. It is described in POSIX as well.
回答4:
Because the library function may not be reentrant.
来源：https://stackoverflow.com/questions/2461583/calling-a-standard-library-function-in-signal-handler