Add workaround for bad QoI posix_spawn()

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

7 files changed, 425 insertions, 268 deletions

diff --git a/src/libstddjb/child_spawn-internal.h b/src/libstddjb/child_spawn-internal.h
new file mode 100644
index 0000000..b0f701c
--- /dev/null
+++ b/src/libstddjb/child_spawn-internal.h
@@ -0,0 +1,16 @@
+/* ISC license. */
+
+#ifndef CHILD_SPAWN_INTERNAL_H
+#define CHILD_SPAWN_INTERNAL_H
+
+#include <skalibs/sysdeps.h>
+
+#ifdef SKALIBS_HASPOSIXSPAWNEARLYRETURN
+
+#include <sys/types.h>
+
+extern pid_t child_spawn_workaround (pid_t, int const *) ;  /* closes the pipe */
+
+#endif
+
+#endif
diff --git a/src/libstddjb/child_spawn.c b/src/libstddjb/child_spawn.c
index aa70deb..e5f5115 100644
--- a/src/libstddjb/child_spawn.c
+++ b/src/libstddjb/child_spawn.c
@@ -3,58 +3,48 @@
 /* MT-unsafe */
 
 #include <skalibs/sysdeps.h>
+
 #include <string.h>
-#include <sys/stat.h>
-#include <fcntl.h>
-#include <sys/wait.h>
-#include <unistd.h>
 #include <errno.h>
-#include <signal.h>
+#include <unistd.h>
+
+#include <skalibs/types.h>
+#include <skalibs/djbunix.h>
 
 #ifdef SKALIBS_HASPOSIXSPAWN
 
+#include <signal.h>
 #include <stdlib.h>
 #include <spawn.h>
-#include <skalibs/config.h>
-
-#else
-
-#include <skalibs/sig.h>
-#include <skalibs/strerr.h>
-#include <skalibs/exec.h>
-
-#endif
 
-#include <skalibs/types.h>
-#include <skalibs/allreadwrite.h>
+#include <skalibs/config.h>
 #include <skalibs/env.h>
-#include <skalibs/djbunix.h>
 
- /*
-    If n = 0 : child's stdin and stdout are the same as the parent's
-    If n >= 1 : pipes between parent and child.
-                Parent reads on even ones, writes on odd ones.
- */
+#ifdef SKALIBS_HASPOSIXSPAWNEARLYRETURN
+# include "child_spawn-internal.h"
+#endif
 
 pid_t child_spawn (char const *prog, char const *const *argv, char const *const *envp, int *fds, unsigned int n)
 {
   pid_t pid ;
-#ifdef SKALIBS_HASPOSIXSPAWN
   posix_spawn_file_actions_t actions ;
   posix_spawnattr_t attr ;
+  sigset_t set ;
   int e ;
-#else
-  int syncpipe[2] ;
-#endif
   int p[n ? n : 1][2] ;
   size_t m = sizeof(SKALIBS_CHILD_SPAWN_FDS_ENVVAR) ;
   unsigned int i = 0 ;
   char modifs[m + 1 + n * UINT_FMT] ;
+#ifdef SKALIBS_HASPOSIXSPAWNEARLYRETURN
+  int syncpipe[2] ;
+  if (pipecoe(syncpipe) == -1) return 0 ;
+#endif
+
   memcpy(modifs, SKALIBS_CHILD_SPAWN_FDS_ENVVAR "=", sizeof(SKALIBS_CHILD_SPAWN_FDS_ENVVAR)) ;
   for (; i < n ; i++)
   {
-    if (pipe(p[i]) < 0) goto errpi ;
-    if ((ndelay_on(p[i][i & 1]) < 0) || (coe(p[i][i & 1]) < 0))
+    if (pipe(p[i]) == -1) goto errpi ;
+    if ((ndelay_on(p[i][i & 1]) == -1) || (coe(p[i][i & 1]) == -1))
     {
       i++ ; goto errpi ;
     }
@@ -66,18 +56,13 @@ pid_t child_spawn (char const *prog, char const *const *argv, char const *const
   }
   modifs[m++] = 0 ;
 
-#ifdef SKALIBS_HASPOSIXSPAWN
-
   e = posix_spawnattr_init(&attr) ;
   if (e) goto erre ;
-  {
-    sigset_t set ;
-    sigemptyset(&set) ;
-    e = posix_spawnattr_setsigmask(&attr, &set) ;
-    if (e) goto errattr ;
-    e = posix_spawnattr_setflags(&attr, POSIX_SPAWN_SETSIGMASK) ;
-    if (e) goto errattr ;
-  }
+  sigemptyset(&set) ;
+  e = posix_spawnattr_setsigmask(&attr, &set) ;
+  if (e) goto errattr ;
+  e = posix_spawnattr_setflags(&attr, POSIX_SPAWN_SETSIGMASK) ;
+  if (e) goto errattr ;
   e = posix_spawn_file_actions_init(&actions) ;
   if (e) goto errattr ;
   if (n >= 2 && p[1][0])
@@ -110,53 +95,104 @@ pid_t child_spawn (char const *prog, char const *const *argv, char const *const
 
   posix_spawn_file_actions_destroy(&actions) ;
   posix_spawnattr_destroy(&attr) ;
+  for (i = 0 ; i < n ; i++) fd_close(p[i][!(i & 1)]) ;
+
+#ifdef SKALIBS_HASPOSIXSPAWNEARLYRETURN
+  pid = child_spawn_workaround(pid, syncpipe) ;
+  if (!pid)
+  {
+    for (i = 0 ; i < n ; i++) fd_close(p[i][i & 1]) ;
+    return 0 ;
+  }
+#endif
+  for (i = 0 ; i < n ; i++) fds[i] = p[i][i & 1] ;
+  return pid ;
+
+ erractions:
+  posix_spawn_file_actions_destroy(&actions) ;
+ errattr:
+  posix_spawnattr_destroy(&attr) ;
+ erre:
+  errno = e ;
+  i = n ;
+ errpi:
+  while (i--)
+  {
+    fd_close(p[i][1]) ;
+    fd_close(p[i][0]) ;
+  }
+#ifdef SKALIBS_HASPOSIXSPAWNEARLYRETURN
+  fd_close(syncpipe[1]) ;
+  fd_close(syncpipe[0]) ;
+#endif
+  return 0 ;
+}
 
 #else
+
+#include <skalibs/allreadwrite.h>
+#include <skalibs/sig.h>
+#include <skalibs/exec.h>
+
+pid_t child_spawn (char const *prog, char const *const *argv, char const *const *envp, int *fds, unsigned int n)
+{
+  pid_t pid ;
+  int syncpipe[2] ;
+  int p[n ? n : 1][2] ;
+  size_t m = sizeof(SKALIBS_CHILD_SPAWN_FDS_ENVVAR) ;
+  unsigned int i = 0 ;
+  char modifs[m + 1 + n * UINT_FMT] ;
+  char c ;
+
+  memcpy(modifs, SKALIBS_CHILD_SPAWN_FDS_ENVVAR "=", sizeof(SKALIBS_CHILD_SPAWN_FDS_ENVVAR)) ;
+  for (; i < n ; i++)
+  {
+    if (pipe(p[i]) == -1) goto errpi ;
+    if ((ndelay_on(p[i][i & 1]) == -1) || (coe(p[i][i & 1]) == -1))
+    {
+      i++ ; goto errpi ;
+    }
+  }
+  for (i = 2 ; i < n ; i++)
+  {
+    m += uint_fmt(modifs + m, p[i][!(i & 1)]) ;
+    if (i+1 < n) modifs[m++] = ',' ;
+  }
+  modifs[m++] = 0 ;
+
   if (pipecoe(syncpipe) < 0) goto errp ;
 
   pid = fork() ;
   if (pid < 0) goto errsp ;
   else if (!pid)
   {
-    size_t len = strlen(PROG) ;
-    char name[len + 9] ;
-    memcpy(name, PROG, len) ;
-    memcpy(name + len, " (child)", 9) ;
-    PROG = name ;
     if (n >= 2)
     {
-      if (fd_move2(0, p[1][0], 1, p[0][1]) < 0) goto syncdie ;
+      if (fd_move2(0, p[1][0], 1, p[0][1]) == -1) goto syncdie ;
     }
     else if (n)
     {
-      if (fd_move(1, p[0][1]) < 0) goto syncdie ;
+      if (fd_move(1, p[0][1]) == -1) goto syncdie ;
     }
     sig_blocknone() ;
     mexec_aen(prog, argv, envp, modifs, m, 1) ;
-
   syncdie:
-    {
-      unsigned char c = errno ;
-      fd_write(syncpipe[1], (char *)&c, 1) ;
-    }
+    c = errno ;
+    fd_write(syncpipe[1], &c, 1) ;
     _exit(127) ;
   }
 
   fd_close(syncpipe[1]) ;
+  syncpipe[1] = fd_read(syncpipe[0], &c, 1) ;
+  if (syncpipe[1])
   {
-    unsigned char c ;
-    syncpipe[1] = fd_read(syncpipe[0], (char *)&c, 1) ;
-    if (syncpipe[1])
-    {
-      int e = c ;
-      if (syncpipe[1] < 0) e = errno ;
-      if (wait_pid(pid, &syncpipe[1]) < 0) e = errno ;
-      errno = e ;
-      goto errsp0 ;
-    }
+    int e = (unsigned char)c ;
+    if (syncpipe[1] == -1) e = errno ;
+    if (wait_pid(pid, 0) == -1) e = errno ;
+    errno = e ;
+    goto errsp0 ;
   }
   fd_close(syncpipe[0]) ;
-#endif
 
   for (i = n ; i ; i--)
   {
@@ -165,21 +201,11 @@ pid_t child_spawn (char const *prog, char const *const *argv, char const *const
   }
   return pid ;
 
-#ifdef SKALIBS_HASPOSIXSPAWN
- erractions:
-  posix_spawn_file_actions_destroy(&actions) ;
- errattr:
-  posix_spawnattr_destroy(&attr) ;
- erre:
-  errno = e ;
-#endif
-#ifndef SKALIBS_HASPOSIXSPAWN
  errsp:
   fd_close(syncpipe[1]) ;
  errsp0:
   fd_close(syncpipe[0]) ;
  errp:
-#endif
   i = n ;
  errpi:
   while (i--)
@@ -189,3 +215,5 @@ pid_t child_spawn (char const *prog, char const *const *argv, char const *const
   }
   return 0 ;
 }
+
+#endif
diff --git a/src/libstddjb/child_spawn0.c b/src/libstddjb/child_spawn0.c
index 5b59b20..cfd78f8 100644
--- a/src/libstddjb/child_spawn0.c
+++ b/src/libstddjb/child_spawn0.c
@@ -1,42 +1,59 @@
 /* ISC license. */
 
 #include <skalibs/sysdeps.h>
+
 #include <errno.h>
 
 #ifdef SKALIBS_HASPOSIXSPAWN
 
 #include <signal.h>
-#include <spawn.h>
 #include <stdlib.h>
+#include <spawn.h>
 
 #include <skalibs/config.h>
 
+#ifdef SKALIBS_HASPOSIXSPAWNEARLYRETURN
+# include <skalibs/djbunix.h>
+# include "child_spawn-internal.h"
+#endif
+
 pid_t child_spawn0 (char const *prog, char const *const *argv, char const *const *envp)
 {
   pid_t pid ;
   posix_spawnattr_t attr ;
+  sigset_t set ;
   int e ;
   int nopath = !getenv("PATH") ;
+#ifdef SKALIBS_HASPOSIXSPAWNEARLYRETURN
+  int p[2] ;
+  if (pipecoe(p) == -1) return 0 ;
+#endif
   e = posix_spawnattr_init(&attr) ;
   if (e) goto err ;
-  {
-    sigset_t set ;
-    sigemptyset(&set) ;
-    e = posix_spawnattr_setsigmask(&attr, &set) ;
-    if (e) goto errattr ;
-    e = posix_spawnattr_setflags(&attr, POSIX_SPAWN_SETSIGMASK) ;
-    if (e) goto errattr ;
-  }
+  sigemptyset(&set) ;
+  e = posix_spawnattr_setsigmask(&attr, &set) ;
+  if (e) goto errattr ;
+  e = posix_spawnattr_setflags(&attr, POSIX_SPAWN_SETSIGMASK) ;
+  if (e) goto errattr ;
   if (nopath && (setenv("PATH", SKALIBS_DEFAULTPATH, 0) < 0)) { e = errno ; goto errattr ; }
   e = posix_spawnp(&pid, prog, 0, &attr, (char *const *)argv, (char *const *)envp) ;
   if (nopath) unsetenv("PATH") ;
+  if (e) goto errattr ;
+
   posix_spawnattr_destroy(&attr) ;
-  if (e) goto err ;
+#ifdef SKALIBS_HASPOSIXSPAWNEARLYRETURN
+  return child_spawn_workaround(pid, p) ;
+#else
   return pid ;
+#endif
 
  errattr:
   posix_spawnattr_destroy(&attr) ;
  err:
+#ifdef SKALIBS_HASPOSIXSPAWNEARLYRETURN
+  fd_close(p[1]) ;
+  fd_close(p[0]) ;
+#endif
   errno = e ;
   return 0 ;
 }
@@ -44,10 +61,8 @@ pid_t child_spawn0 (char const *prog, char const *const *argv, char const *const
 #else
 
 #include <unistd.h>
-#include <string.h>
 
 #include <skalibs/allreadwrite.h>
-#include <skalibs/strerr.h>
 #include <skalibs/sig.h>
 #include <skalibs/djbunix.h>
 #include <skalibs/exec.h>
@@ -56,8 +71,9 @@ pid_t child_spawn0 (char const *prog, char const *const *argv, char const *const
 {
   pid_t pid ;
   int p[2] ;
-  unsigned char c ;
-  if (pipecoe(p) < 0) return 0 ;
+  char c ;
+
+  if (pipecoe(p) == -1) return 0 ;
   pid = fork() ;
   if (pid < 0)
   {
@@ -67,20 +83,14 @@ pid_t child_spawn0 (char const *prog, char const *const *argv, char const *const
   }
   if (!pid)
   {
-    size_t len = strlen(PROG) ;
-    char name[len + 9] ;
-    memcpy(name, PROG, len) ;
-    memcpy(name + len, " (child)", 9) ;
-    PROG = name ;
-    fd_close(p[0]) ;
     sig_blocknone() ;
     exec_ae(prog, argv, envp) ;
     c = errno ;
-    fd_write(p[1], (char *)&c, 1) ;
+    fd_write(p[1], &c, 1) ;
     _exit(127) ;
   }
   fd_close(p[1]) ;
-  p[1] = fd_read(p[0], (char *)&c, 1) ;
+  p[1] = fd_read(p[0], &c, 1) ;
   if (p[1] < 0)
   {
     fd_close(p[0]) ;
@@ -90,7 +100,7 @@ pid_t child_spawn0 (char const *prog, char const *const *argv, char const *const
   if (p[1])
   {
     wait_pid(pid, &p[0]) ;
-    errno = c ;
+    errno = (unsigned char)c ;
     return 0 ;
   }
   return pid ;
diff --git a/src/libstddjb/child_spawn1_internal.c b/src/libstddjb/child_spawn1_internal.c
index be154f0..2fe0ee2 100644
--- a/src/libstddjb/child_spawn1_internal.c
+++ b/src/libstddjb/child_spawn1_internal.c
@@ -1,9 +1,11 @@
 /* ISC license. */
 
 #include <skalibs/sysdeps.h>
-#include <unistd.h>
+
 #include <errno.h>
 
+#include <skalibs/djbunix.h>
+
 #ifdef SKALIBS_HASPOSIXSPAWN
 
 #include <signal.h>
@@ -11,26 +13,33 @@
 #include <stdlib.h>
 
 #include <skalibs/config.h>
-#include <skalibs/djbunix.h>
+
+#ifdef SKALIBS_HASPOSIXSPAWNEARLYRETURN
+# include "child_spawn-internal.h"
+#endif
 
 pid_t child_spawn1_internal (char const *prog, char const *const *argv, char const *const *envp, int *p, int to)
 {
   pid_t pid ;
   posix_spawn_file_actions_t actions ;
   posix_spawnattr_t attr ;
+  sigset_t set ;
   int e ;
   int nopath = !getenv("PATH") ;
-  if (coe(p[!(to & 1)]) < 0) goto err ;
+
+#ifdef SKALIBS_HASPOSIXSPAWNEARLYRETURN
+  int syncpipe[2] ;
+  if (pipecoe(syncpipe) == -1) goto err ;
+#endif
+
+  if (coe(p[!(to & 1)]) == -1) goto errp ;
   e = posix_spawnattr_init(&attr) ;
   if (e) goto erre ;
-  {
-    sigset_t set ;
-    sigemptyset(&set) ;
-    e = posix_spawnattr_setsigmask(&attr, &set) ;
-    if (e) goto errattr ;
-    e = posix_spawnattr_setflags(&attr, POSIX_SPAWN_SETSIGMASK) ;
-    if (e) goto errattr ;
-  }
+  sigemptyset(&set) ;
+  e = posix_spawnattr_setsigmask(&attr, &set) ;
+  if (e) goto errattr ;
+  e = posix_spawnattr_setflags(&attr, POSIX_SPAWN_SETSIGMASK) ;
+  if (e) goto errattr ;
   e = posix_spawn_file_actions_init(&actions) ;
   if (e) goto errattr ;
   if (p[to & 1] != (to & 1))
@@ -49,10 +58,16 @@ pid_t child_spawn1_internal (char const *prog, char const *const *argv, char con
   e = posix_spawnp(&pid, prog, &actions, &attr, (char *const *)argv, (char *const *)envp) ;
   if (nopath) unsetenv("PATH") ;
   if (e) goto erractions ;
+
   posix_spawn_file_actions_destroy(&actions) ;
   posix_spawnattr_destroy(&attr) ;
   fd_close(p[to & 1]) ;
+
+#ifdef SKALIBS_HASPOSIXSPAWNEARLYRETURN
+  return child_spawn_workaround(pid, syncpipe) ;
+#else
   return pid ;
+#endif
 
  erractions:
   posix_spawn_file_actions_destroy(&actions) ;
@@ -60,7 +75,12 @@ pid_t child_spawn1_internal (char const *prog, char const *const *argv, char con
   posix_spawnattr_destroy(&attr) ;
  erre:
   errno = e ;
+ errp:
+#ifdef SKALIBS_HASPOSIXSPAWNEARLYRETURN
+  fd_close(syncpipe[1]) ;
+  fd_close(syncpipe[0]) ;
  err:
+#endif
   fd_close(p[1]) ;
   fd_close(p[0]) ;
   return 0 ;
@@ -68,59 +88,46 @@ pid_t child_spawn1_internal (char const *prog, char const *const *argv, char con
 
 #else
 
-#include <string.h>
+#include <unistd.h>
 
 #include <skalibs/allreadwrite.h>
-#include <skalibs/strerr.h>
 #include <skalibs/sig.h>
-#include <skalibs/djbunix.h>
 #include <skalibs/exec.h>
 
 pid_t child_spawn1_internal (char const *prog, char const *const *argv, char const *const *envp, int *p, int to)
 {
   pid_t pid ;
   int syncpipe[2] ;
+  char c ;
+
   if (coe(p[0]) < 0 || pipecoe(syncpipe) < 0) goto err ;
 
   pid = fork() ;
   if (pid < 0) goto errsp ;
   if (!pid)
   {
-    size_t len = strlen(PROG) ;
-    char name[len + 9] ;
-    memcpy(name, PROG, len) ;
-    memcpy(name + len, " (child)", 9) ;
-    PROG = name ;
     fd_close(p[!(to & 1)]) ;
     if (fd_move(to & 1, p[to & 1]) < 0) goto syncdie ;
     if ((to & 2) && (fd_copy(!(to & 1), to & 1) < 0)) goto syncdie ;
     sig_blocknone() ;
     exec_ae(prog, argv, envp) ;
-
    syncdie:
-    {
-      unsigned char c = errno ;
-      fd_write(syncpipe[1], (char *)&c, 1) ;
-    }
+    c = errno ;
+    fd_write(syncpipe[1], &c, 1) ;
     _exit(127) ;
   }
 
   fd_close(syncpipe[1]) ;
-
+  syncpipe[1] = fd_read(syncpipe[0], &c, 1) ;
+  if (syncpipe[1])
   {
-    unsigned char c ;
-    syncpipe[1] = fd_read(syncpipe[0], (char *)&c, 1) ;
-    if (syncpipe[1])
-    {
-      int e = c ;
-      if (syncpipe[1] < 0) e = errno ;
-      if (wait_pid(pid, &syncpipe[1]) < 0) e = errno ;
-      errno = e ;
-      goto errsp0 ;
-    }
+    int e = (unsigned char)c ;
+    if (syncpipe[1] == -1) e = errno ;
+    if (wait_pid(pid, 0) == -1) e = errno ;
+    errno = e ;
+    goto errsp0 ;
   }
   fd_close(syncpipe[0]) ;
-
   fd_close(p[to & 1]) ;
   return pid ;
 
diff --git a/src/libstddjb/child_spawn2.c b/src/libstddjb/child_spawn2.c
index bddd97f..44d748f 100644
--- a/src/libstddjb/child_spawn2.c
+++ b/src/libstddjb/child_spawn2.c
@@ -3,58 +3,48 @@
 /* MT-unsafe */
 
 #include <skalibs/sysdeps.h>
-#include <sys/stat.h>
-#include <fcntl.h>
-#include <sys/wait.h>
+
 #include <unistd.h>
 #include <errno.h>
-#include <signal.h>
+
+#include <skalibs/djbunix.h>
 
 #ifdef SKALIBS_HASPOSIXSPAWN
 
+#include <signal.h>
 #include <stdlib.h>
 #include <spawn.h>
-#include <skalibs/config.h>
 
-#else
-
-#include <string.h>
-#include <skalibs/allreadwrite.h>
-#include <skalibs/sig.h>
-#include <skalibs/strerr.h>
-#include <skalibs/exec.h>
+#include <skalibs/config.h>
 
+#ifdef SKALIBS_HASPOSIXSPAWNEARLYRETURN
+# include "child_spawn-internal.h"
 #endif
 
-#include <skalibs/djbunix.h>
-
 pid_t child_spawn2 (char const *prog, char const *const *argv, char const *const *envp, int *fds)
 {
   pid_t pid ;
-#ifdef SKALIBS_HASPOSIXSPAWN
   posix_spawn_file_actions_t actions ;
   posix_spawnattr_t attr ;
+  int p[2][2] ;
   int e ;
-#else
+  int nopath = !getenv("PATH") ;
+  sigset_t set ;
+#ifdef SKALIBS_HASPOSIXSPAWNEARLYRETURN
   int syncpipe[2] ;
+  if (pipecoe(syncpipe) == -1) return 0 ;
 #endif
-  int p[2][2] ;
-  if (pipe(p[0]) < 0) return 0 ;
-  if (ndelay_on(p[0][0]) < 0 || coe(p[0][0]) < 0 || pipe(p[1]) < 0) goto errp ;
-  if (ndelay_on(p[1][1]) < 0 || coe(p[1][1]) < 0) goto errp1 ;
-
-#ifdef SKALIBS_HASPOSIXSPAWN
+  if (pipe(p[0]) == -1) goto err ;
+  if (ndelay_on(p[0][0]) == -1 || coe(p[0][0]) == -1 || pipe(p[1]) == -1) goto errp ;
+  if (ndelay_on(p[1][1]) == -1 || coe(p[1][1]) == -1) goto errp1 ;
 
   e = posix_spawnattr_init(&attr) ;
   if (e) goto erre ;
-  {
-    sigset_t set ;
-    sigemptyset(&set) ;
-    e = posix_spawnattr_setsigmask(&attr, &set) ;
-    if (e) goto errattr ;
-    e = posix_spawnattr_setflags(&attr, POSIX_SPAWN_SETSIGMASK) ;
-    if (e) goto errattr ;
-  }
+  sigemptyset(&set) ;
+  e = posix_spawnattr_setsigmask(&attr, &set) ;
+  if (e) goto errattr ;
+  e = posix_spawnattr_setflags(&attr, POSIX_SPAWN_SETSIGMASK) ;
+  if (e) goto errattr ;
   e = posix_spawn_file_actions_init(&actions) ;
   if (e) goto errattr ;
   if (p[1][0] != fds[0])
@@ -71,78 +61,105 @@ pid_t child_spawn2 (char const *prog, char const *const *argv, char const *const
     e = posix_spawn_file_actions_addclose(&actions, p[0][1]) ;
     if (e) goto erractions ;
   }
+  if (nopath && (setenv("PATH", SKALIBS_DEFAULTPATH, 0) == -1))
   {
-    int nopath = !getenv("PATH") ;
-    if (nopath && (setenv("PATH", SKALIBS_DEFAULTPATH, 0) < 0))
-    {
-      e = errno ; goto erractions ;
-    }
-    e = posix_spawnp(&pid, prog, &actions, &attr, (char *const *)argv, (char *const *)envp) ;
-    if (nopath) unsetenv("PATH") ;
-    if (e) goto erractions ;
+    e = errno ; goto erractions ;
+  }
+  e = posix_spawnp(&pid, prog, &actions, &attr, (char *const *)argv, (char *const *)envp) ;
+  if (nopath) unsetenv("PATH") ;
+  if (e) goto erractions ;
+
+  posix_spawn_file_actions_destroy(&actions) ;
+  posix_spawnattr_destroy(&attr) ;
+  fd_close(p[0][1]) ;
+  fd_close(p[1][0]) ;
+
+#ifdef SKALIBS_HASPOSIXSPAWNEARLYRETURN
+  pid = child_spawn_workaround(pid, syncpipe) ;
+  if (!pid)
+  {
+    fd_close(p[1][1]) ;
+    fd_close(p[0][0]) ;
+    return 0 ;
   }
+#endif
+  fds[0] = p[0][0] ;
+  fds[1] = p[1][1] ;
+  return pid ;
 
+ erractions:
   posix_spawn_file_actions_destroy(&actions) ;
+ errattr:
   posix_spawnattr_destroy(&attr) ;
+ erre:
+  errno = e ;
+ errp1:
+  fd_close(p[1][1]) ;
+  fd_close(p[1][0]) ;
+ errp:
+  fd_close(p[0][1]) ;
+  fd_close(p[0][0]) ;
+ err:
+#ifdef SKALIBS_HASPOSIXSPAWNEARLYRETURN
+  fd_close(syncpipe[1]) ;
+  fd_close(syncpipe[0]) ;
+#endif
+  return 0 ;
+}
 
 #else
+
+#include <skalibs/allreadwrite.h>
+#include <skalibs/sig.h>
+#include <skalibs/exec.h>
+
+pid_t child_spawn2 (char const *prog, char const *const *argv, char const *const *envp, int *fds)
+{
+  pid_t pid ;
+  int syncpipe[2] ;
+  int p[2][2] ;
+  char c ;
+
+  if (pipe(p[0]) < 0) return 0 ;
+  if (ndelay_on(p[0][0]) < 0 || coe(p[0][0]) < 0 || pipe(p[1]) < 0) goto errp ;
+  if (ndelay_on(p[1][1]) < 0 || coe(p[1][1]) < 0) goto errp1 ;
   if (pipecoe(syncpipe) < 0) goto errp1 ;
 
   pid = fork() ;
-  if (pid < 0) goto errsp ;
+  if (pid == -1) goto errsp ;
   else if (!pid)
   {
-    size_t len = strlen(PROG) ;
-    char name[len + 9] ;
-    memcpy(name, PROG, len) ;
-    memcpy(name + len, " (child)", 9) ;
-    PROG = name ;
     if (fd_move2(fds[0], p[1][0], fds[1], p[0][1]) < 0) goto syncdie ;
     sig_blocknone() ;
     exec_ae(prog, argv, envp) ;
-
-  syncdie:
-    {
-      unsigned char c = errno ;
-      fd_write(syncpipe[1], (char *)&c, 1) ;
-    }
+   syncdie:
+    c = errno ;
+    fd_write(syncpipe[1], &c, 1) ;
     _exit(127) ;
   }
 
   fd_close(syncpipe[1]) ;
+  syncpipe[1] = fd_read(syncpipe[0], &c, 1) ;
+  if (syncpipe[1])
   {
-    unsigned char c ;
-    syncpipe[1] = fd_read(syncpipe[0], (char *)&c, 1) ;
-    if (syncpipe[1])
-    {
-      int e = c ;
-      if (syncpipe[1] < 0) e = errno ;
-      if (wait_pid(pid, &syncpipe[1]) < 0) e = errno ;
-      errno = e ;
-      goto errsp0 ;
-    }
+    int e = (unsigned char)c ;
+    if (syncpipe[1] == -1) e = errno ;
+    if (wait_pid(pid, &syncpipe[1]) == -1) e = errno ;
+    errno = e ;
+    goto errsp0 ;
   }
   fd_close(syncpipe[0]) ;
-#endif
+  fd_close(p[0][1]) ;
+  fd_close(p[1][0]) ;
 
-  fd_close(p[0][1]) ; fds[0] = p[0][0] ;
-  fd_close(p[1][0]) ; fds[1] = p[1][1] ;
+  fds[0] = p[0][0] ;
+  fds[1] = p[1][1] ;
   return pid ;
 
-#ifdef SKALIBS_HASPOSIXSPAWN
- erractions:
-  posix_spawn_file_actions_destroy(&actions) ;
- errattr:
-  posix_spawnattr_destroy(&attr) ;
- erre:
-  errno = e ;
-#endif
-#ifndef SKALIBS_HASPOSIXSPAWN
  errsp:
   fd_close(syncpipe[1]) ;
  errsp0:
   fd_close(syncpipe[0]) ;
-#endif
  errp1:
   fd_close(p[1][1]) ;
   fd_close(p[1][0]) ;
@@ -151,3 +168,5 @@ pid_t child_spawn2 (char const *prog, char const *const *argv, char const *const
   fd_close(p[0][0]) ;
   return 0 ;
 }
+
+#endif
diff --git a/src/libstddjb/child_spawn3.c b/src/libstddjb/child_spawn3.c
index 733df74..81ffb0c 100644
--- a/src/libstddjb/child_spawn3.c
+++ b/src/libstddjb/child_spawn3.c
@@ -3,64 +3,54 @@
 /* MT-unsafe */
 
 #include <skalibs/sysdeps.h>
-#include <sys/stat.h>
-#include <fcntl.h>
-#include <sys/wait.h>
+
 #include <unistd.h>
 #include <errno.h>
-#include <signal.h>
+
+#include <skalibs/types.h>
+#include <skalibs/djbunix.h>
 
 #ifdef SKALIBS_HASPOSIXSPAWN
 
+#include <signal.h>
 #include <stdlib.h>
 #include <spawn.h>
-#include <skalibs/config.h>
-
-#else
 
-#include <string.h>
-#include <skalibs/sig.h>
-#include <skalibs/strerr.h>
-#include <skalibs/exec.h>
+#include <skalibs/config.h>
+#include <skalibs/env.h>
 
+#ifdef SKALIBS_HASPOSIXSPAWNEARLYRETURN
+# include "child_spawn-internal.h"
 #endif
 
-#include <skalibs/types.h>
-#include <skalibs/allreadwrite.h>
-#include <skalibs/env.h>
-#include <skalibs/djbunix.h>
-
 pid_t child_spawn3 (char const *prog, char const *const *argv, char const *const *envp, int *fds)
 {
   pid_t pid ;
-#ifdef SKALIBS_HASPOSIXSPAWN
   posix_spawn_file_actions_t actions ;
   posix_spawnattr_t attr ;
+  sigset_t set ;
   int e ;
-#else
-  int syncpipe[2] ;
-#endif
   int p[3][2] ;
   size_t m = sizeof(SKALIBS_CHILD_SPAWN_FDS_ENVVAR) ;
   char modifs[sizeof(SKALIBS_CHILD_SPAWN_FDS_ENVVAR) + UINT_FMT] = SKALIBS_CHILD_SPAWN_FDS_ENVVAR "=" ;
-  if (pipe(p[0]) < 0 || ndelay_on(p[0][0]) < 0 || coe(p[0][0]) < 0) return 0 ;
+#ifdef SKALIBS_HASPOSIXSPAWNEARLYRETURN
+  int syncpipe[2] ;
+  if (pipecoe(syncpipe) == -1) return 0 ;
+#endif
+
+  if (pipe(p[0]) < 0 || ndelay_on(p[0][0]) < 0 || coe(p[0][0]) < 0) goto err ;
   if (pipe(p[1]) < 0 || ndelay_on(p[1][1]) < 0 || coe(p[1][1]) < 0) goto errp0 ;
   if (pipe(p[2]) < 0 || ndelay_on(p[2][0]) < 0 || coe(p[2][0]) < 0) goto errp1 ;
   m += uint_fmt(modifs + sizeof(SKALIBS_CHILD_SPAWN_FDS_ENVVAR), p[2][1]) ;
   modifs[m++] = 0 ;
 
-#ifdef SKALIBS_HASPOSIXSPAWN
-
   e = posix_spawnattr_init(&attr) ;
   if (e) goto erre ;
-  {
-    sigset_t set ;
-    sigemptyset(&set) ;
-    e = posix_spawnattr_setsigmask(&attr, &set) ;
-    if (e) goto errattr ;
-    e = posix_spawnattr_setflags(&attr, POSIX_SPAWN_SETSIGMASK) ;
-    if (e) goto errattr ;
-  }
+  sigemptyset(&set) ;
+  e = posix_spawnattr_setsigmask(&attr, &set) ;
+  if (e) goto errattr ;
+  e = posix_spawnattr_setflags(&attr, POSIX_SPAWN_SETSIGMASK) ;
+  if (e) goto errattr ;
   e = posix_spawn_file_actions_init(&actions) ;
   if (e) goto errattr ;
   if (p[1][0] != fds[0])
@@ -77,7 +67,7 @@ pid_t child_spawn3 (char const *prog, char const *const *argv, char const *const
     e = posix_spawn_file_actions_addclose(&actions, p[0][1]) ;
     if (e) goto erractions ;
   }
-  {
+  { 
     int nopath = !getenv("PATH") ;
     size_t envlen = env_len(envp) ;
     char const *newenv[envlen + 2] ;
@@ -93,46 +83,93 @@ pid_t child_spawn3 (char const *prog, char const *const *argv, char const *const
 
   posix_spawn_file_actions_destroy(&actions) ;
   posix_spawnattr_destroy(&attr) ;
+  fd_close(p[2][1]) ;
+  fd_close(p[1][0]) ;
+  fd_close(p[0][1]) ;
+
+#ifdef SKALIBS_HASPOSIXSPAWNEARLYRETURN
+  pid = child_spawn_workaround(pid, syncpipe) ;
+  if (!pid)
+  {
+    fd_close(p[2][0]) ;
+    fd_close(p[1][1]) ;
+    fd_close(p[0][0]) ;
+    return 0 ;
+  }
+#endif
+  fds[0] = p[0][0] ;
+  fds[1] = p[1][1] ;
+  fds[2] = p[2][0] ;
+  return pid ;
+
+ erractions:
+  posix_spawn_file_actions_destroy(&actions) ;
+ errattr:
+  posix_spawnattr_destroy(&attr) ;
+ erre:
+  errno = e ;
+  fd_close(p[2][1]) ;
+  fd_close(p[2][0]) ;
+ errp1:
+  fd_close(p[1][1]) ;
+  fd_close(p[1][0]) ;
+ errp0:
+  fd_close(p[0][1]) ;
+  fd_close(p[0][0]) ;
+ err:
+#ifdef SKALIBS_HASPOSIXSPAWNEARLYRETURN
+  fd_close(syncpipe[1]) ;
+  fd_close(syncpipe[0]) ;
+#endif
+  return 0 ;
+}
 
 #else
+
+#include <skalibs/allreadwrite.h>
+#include <skalibs/sig.h>
+#include <skalibs/exec.h>
+
+pid_t child_spawn3 (char const *prog, char const *const *argv, char const *const *envp, int *fds)
+{
+  pid_t pid ;
+  int syncpipe[2] ;
+  int p[3][2] ;
+  size_t m = sizeof(SKALIBS_CHILD_SPAWN_FDS_ENVVAR) ;
+  char modifs[sizeof(SKALIBS_CHILD_SPAWN_FDS_ENVVAR) + UINT_FMT] = SKALIBS_CHILD_SPAWN_FDS_ENVVAR "=" ;
+  char c ;
+
+  if (pipe(p[0]) == -1 || ndelay_on(p[0][0]) == -1 || coe(p[0][0]) == -1) return 0 ;
+  if (pipe(p[1]) == -1 || ndelay_on(p[1][1]) == -1 || coe(p[1][1]) == -1) goto errp0 ;
+  if (pipe(p[2]) == -1 || ndelay_on(p[2][0]) == -1 || coe(p[2][0]) == -1) goto errp1 ;
+  m += uint_fmt(modifs + sizeof(SKALIBS_CHILD_SPAWN_FDS_ENVVAR), p[2][1]) ;
+  modifs[m++] = 0 ;
   if (pipecoe(syncpipe) < 0) goto errp2 ;
 
   pid = fork() ;
   if (pid < 0) goto errsp ;
   else if (!pid)
   {
-    size_t len = strlen(PROG) ;
-    char name[len + 9] ;
-    memcpy(name, PROG, len) ;
-    memcpy(name + len, " (child)", 9) ;
-    PROG = name ;
-    if (fd_move2(fds[0], p[1][0], fds[1], p[0][1]) < 0) goto syncdie ;
+    if (fd_move2(fds[0], p[1][0], fds[1], p[0][1]) == -1) goto syncdie ;
     sig_blocknone() ;
     mexec_aen(prog, argv, envp, modifs, m, 1) ;
-
-  syncdie:
-    {
-      unsigned char c = errno ;
-      fd_write(syncpipe[1], (char *)&c, 1) ;
-    }
+   syncdie:
+    c = errno ;
+    fd_write(syncpipe[1], &c, 1) ;
     _exit(127) ;
   }
 
   fd_close(syncpipe[1]) ;
+  syncpipe[1] = fd_read(syncpipe[0], &c, 1) ;
+  if (syncpipe[1])
   {
-    unsigned char c ;
-    syncpipe[1] = fd_read(syncpipe[0], (char *)&c, 1) ;
-    if (syncpipe[1])
-    {
-      int e = c ;
-      if (syncpipe[1] < 0) e = errno ;
-      if (wait_pid(pid, &syncpipe[1]) < 0) e = errno ;
-      errno = e ;
-      goto errsp0 ;
-    }
+    int e = (unsigned char)c ;
+    if (syncpipe[1] == -1) e = errno ;
+    if (wait_pid(pid, &syncpipe[1]) == -1) e = errno ;
+    errno = e ;
+    goto errsp0 ;
   }
   fd_close(syncpipe[0]) ;
-#endif
 
   fd_close(p[2][1]) ;
   fd_close(p[1][0]) ;
@@ -142,21 +179,11 @@ pid_t child_spawn3 (char const *prog, char const *const *argv, char const *const
   fds[2] = p[2][0] ;
   return pid ;
 
-#ifdef SKALIBS_HASPOSIXSPAWN
- erractions:
-  posix_spawn_file_actions_destroy(&actions) ;
- errattr:
-  posix_spawnattr_destroy(&attr) ;
- erre:
-  errno = e ;
-#endif
-#ifndef SKALIBS_HASPOSIXSPAWN
  errsp:
   fd_close(syncpipe[1]) ;
  errsp0:
   fd_close(syncpipe[0]) ;
  errp2:
-#endif
   fd_close(p[2][1]) ;
   fd_close(p[2][0]) ;
  errp1:
@@ -167,3 +194,5 @@ pid_t child_spawn3 (char const *prog, char const *const *argv, char const *const
   fd_close(p[0][0]) ;
   return 0 ;
 }
+
+#endif
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