Paul Joselow <pjoselow@xxxxxxxxxxxxx> writes: > I work at a company that uses pthreads. I have some questions about what > this option actually does during a compile. There are cases where even > though a program uses pthreads, the option was omitted from the compile and > build and the program builds successfully. So the questions involve what > things will and will not work when the pthread option is used or omitted. > This is a question I would like to answer across several architectures, > specifically Alpha, Intel Linux, and Solaris. > > I have been shown a case where common variables (e.g. errno) that should be > local to each thread end up being shared across all threads if the pthread > option is omitted. What are the problems with always using the pthread > option on all compiles and links regardless of whether a program uses > pthreads or not? In typical cases, the gcc -pthread option does a #define of _REENTRANT and causes gcc to link against -lpthread. That's it. The library header files will typically act slightly different via #ifdef _REENTRANT. Changing the declaration of errno is a typical case. It's not surprising that some code works if you don't use -pthread. Ian
