Details
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Bug
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Status: Closed
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Major
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Resolution: Fixed
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proton-0.12.2, proton-0.13.0
Description
For some time, we were having random errors on Solaris with proton-c where we would get a transport error "proton:io connect: Error 0". We were finally able to reproduce it in a multi-threading environment. It turns out some C/C++ system calls such as opening sockets will set the value of "errno" and some parts of proton-c code you rely on the value of errno to determine if the operation was successful or not[1].
The issue is that errno is not thread safe[2] and as a consequence if by the time Thread A was checking the value of errno, Thread B has set it to something else, the check will fail.
We resolved it by compiling Proton with "-D_REENTRANT" which makes errno thread local variable.
Please note we only got this error on Solaris because on Linux setting "-lpthread" implies "-D_REENTRANT flag" according to stackoverflow[2].
Do you think this flag could be set by default in the CMakeList of proton to avoid others having the same issue?
On Solaris:
/usr/include/errno.h
#if defined(_REENTRANT) || defined(_TS_ERRNO) || _POSIX_C_SOURCE - 0 >= 199506L
extern int *___errno();
#define errno (*(___errno()))
#else
extern int errno;
/* ANSI C++ requires that errno be a macro */
#if __cplusplus >= 199711L
#define errno errno
#endif
#endif /* defined(_REENTRANT) || defined(_TS_ERRNO) */
PS: The code is still the same on 0.14.0. So the error could happen there as well I guess.
[1]: https://github.com/apache/qpid-proton/blob/0.12.2/proton-c/src/posix/io.c (line 187-188)
[2]: http://stackoverflow.com/questions/1694164/is-errno-thread-safe
[3]: http://stackoverflow.com/questions/875789/gcc-do-i-need-d-reentrant-with-pthreads
Attachments
Issue Links
- relates to
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PROTON-1316 Add a way to set visibility of exportable symbols on Solaris
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- Closed
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