avoid cancellation in pclose

at the point pclose might receive and act on cancellation, it has
already invalidated the FILE passed to it. thus, per musl's QOI
guarantees about cancellation and resource allocation/deallocation,
it's not a candidate for cancellation.

if it were required to be a cancellation point by posix, we would have
to switch the order of deallocation, but somehow still close the pipe
in order to trigger the child process to exit. i looked into doing
this, but the logic gets ugly, and i'm not sure the semantics are
conformant, so i'd rather just leave it alone unless there's a need to
change it.

diff --git a/src/stdio/pclose.c b/src/stdio/pclose.c
index 7c7779663e2dd6c191311e5e2cbf65340b00a7a9..7fb76ed42622f92f2cdb3a8f9ee04bc583d43db8 100644 (file)
--- a/src/stdio/pclose.c
+++ b/src/stdio/pclose.c
@@ -1,11 +1,12 @@
 #include "stdio_impl.h"
+#include "syscall.h"
 
 int pclose(FILE *f)
 {
-       int status;
+       int status, r;
        pid_t pid = f->pipe_pid;
        fclose(f);
-       while (waitpid(pid, &status, 0) == -1)
-               if (errno != EINTR) return -1;
+       while ((r=__syscall(SYS_wait4, pid, &status, 0, 0)) == -EINTR);
+       if (r<0) return __syscall_ret(r);
        return status;
 }