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On Tue, Jan 11, 2005 at 02:21:22PM +0100, Rainer Hochreiter wrote: > > On Mon, Jan 10, 2005 at 08:56:58AM +0100, Rainer Hochreiter wrote: > >> but what's the real reason why popen() results in the address > >> conflict and system() does not?! > > > > AFAICT, popen() calls fork() and system() does not. > > this is not true - both functions call vfork()! > > cygwin-1.5.12-1/newlib/libc/stdlib/system.c:165 if ((pid = vfork ()) == 0) AFAICT, Cygwin's system() is implemented in: winsup/cygwin/syscalls.cc > system() calls execve() while popen() calls execl() to start execution > of another file! Nevertheless, the above is not quite right. fork() is called, but the call occurs in sh *not* the original application. See the attached testcase, st.c, and the following strace snippets: $ strace st | egrep '(Program name| fork):' Program name: c:\home\jtishler\src\c++\st.exe (2788) Program name: C:\cygwin\bin\sh.exe (928) 227 17561 [main] sh 928 fork: entering Program name: C:\cygwin\bin\sh.exe (4948) 199 42119 [main] sh 928 fork: 4948 = fork() 151 43337 [main] sh 4948 fork: 0 = fork() Program name: C:\cygwin\bin\id.exe (4948) This is why system() does not trigger the base address conflict problem and popen() does. Jason -- PGP/GPG Key: http://www.tishler.net/jason/pubkey.asc or key servers Fingerprint: 7A73 1405 7F2B E669 C19D 8784 1AFD E4CC ECF4 8EF6
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st.c
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