Hi Bruno, On 11.05.20 18:37, Bruno Haible wrote: > Hi Tim, > >> i would like to ask for your expert knowledge. >> >> How to prevent file descriptor leaks in a multi-threaded application >> that fork+exec. Quick answer is surely "use O_CLOEXEC" to close those >> file descriptors on exec. >> >> But how does this work with fopen in a portable way ? >> GNU libc has the 'e' flag for exactly this. > > Yes [1]. > >> How about other non-GNU OSes / alternative C libraries ? > > POSIX [2][3], macOS [4], FreeBSD [5], Solaris [6] don't support this 'e' flag. > > How about using open() with O_CLOEXEC, and then fdopen()?
Thanks. Sure, this is possible. Doing so at dozens of places (or more) asks for an implementation in gnulib :) Several projects (most library code) could benefit. I currently think about GnuTLS where we have to fix this in one or the other way. Updating gnulib and adding 'e' to the fopen modes would be straight forward. > > Bruno > > [1] http://man7.org/linux/man-pages/man3/fopen.3.html > [2] https://pubs.opengroup.org/onlinepubs/9699919799/functions/fopen.html > [3] http://man7.org/linux/man-pages/man3/fopen.3p.html > [4] > https://developer.apple.com/library/archive/documentation/System/Conceptual/ManPages_iPhoneOS/man3/fopen.3.html > [5] > https://www.freebsd.org/cgi/man.cgi?query=fopen&sektion=3&apropos=0&manpath=freebsd > [6] https://docs.oracle.com/cd/E36784_01/html/E36874/fopen-3c.html > >
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