Add workaround for bad QoI posix_spawn()

Signed-off-by: Laurent Bercot <ska@appnovation.com>

1 files changed, 48 insertions, 0 deletions

diff --git a/src/libstddjb/child_spawn_workaround.c b/src/libstddjb/child_spawn_workaround.c
new file mode 100644
index 0000000..00f8553
--- /dev/null
+++ b/src/libstddjb/child_spawn_workaround.c
@@ -0,0 +1,48 @@
+/* ISC license. */
+
+#include <skalibs/sysdeps.h>
+
+#if defined(SKALIBS_HASPOSIXSPAWN) && defined(SKALIBS_HASPOSIXSPAWNEARLYRETURN)
+
+#include <errno.h>
+#include <signal.h>
+#include <sys/wait.h>
+
+#include <skalibs/allreadwrite.h>
+#include <skalibs/djbunix.h>
+#include "child_spawn-internal.h"
+
+pid_t child_spawn_workaround (pid_t pid, int const *p)
+{
+  siginfo_t si ;
+  int e ;
+  ssize_t r ;
+  char c ;
+
+  fd_close(p[1]) ;
+  r = fd_read(p[0], &c, 1) ;
+  fd_close(p[0]) ;
+  if (r == -1) return 0 ;
+  if (r) return (errno = EILSEQ, 0) ;  /* child wrote, wtf */
+
+  do e = waitid(P_PID, pid, &si, WNOHANG | WNOWAIT) ;
+  while (e == -1 && errno == EINTR) ;
+  if (e == -1) return pid ;  /* we're in trouble, but don't leak a child */
+  if (!si.si_pid) return pid ;  /* child is running */
+  if (si.si_code != CLD_EXITED || si.si_status != 127) return pid ; /* child died after execve(), let caller handle it */
+  /*
+    child exited 127, so either execve() failed, which is what we want to catch,
+    or it raced like a mofo, execve()d and then exited 127 on its own, in which
+    case, tough luck, it never existed.
+  */
+  wait_pid(pid, 0) ;
+  return (errno = 0, 0) ;
+}
+
+#else
+
+ /* avoid empty TUs */
+
+extern int skalibs_child_spawn_workaround_dummy_ ;
+
+#endif