[PATCH v3 1/2] linux: wait4: Fix incorrect return value comparison

[Alistair Francis <alistair.francis@wdc.com>]

Patch 600f00b "linux: Use long time_t for wait4/getrusage" introduced
two bugs:
 - The usage32 struct was set if the wait4 syscall had an error.
 - For 32-bit systems the usage struct was set even if it was specified
   as NULL.

This patch fixes the two issues.
---
 sysdeps/unix/sysv/linux/wait4.c | 32 ++++++++++++++++++++------------
 1 file changed, 20 insertions(+), 12 deletions(-)

diff --git a/sysdeps/unix/sysv/linux/wait4.c b/sysdeps/unix/sysv/linux/wait4.c
index d14bd4da27..21eb154b72 100644
--- a/sysdeps/unix/sysv/linux/wait4.c
+++ b/sysdeps/unix/sysv/linux/wait4.c
@@ -29,14 +29,18 @@ __wait4_time64 (pid_t pid, int *stat_loc, int options, struct __rusage64 *usage)
 # if __KERNEL_OLD_TIMEVAL_MATCHES_TIMEVAL64
   return SYSCALL_CANCEL (wait4, pid, stat_loc, options, usage);
 # else
-  struct __rusage32 usage32;
-  pid_t ret = SYSCALL_CANCEL (wait4, pid, stat_loc, options, &usage32);
-
-  if (ret != 0)
-    return ret;
+  pid_t ret;
 
   if (usage != NULL)
-    rusage32_to_rusage64 (&usage32, usage);
+    {
+      struct __rusage32 usage32;
+        ret = SYSCALL_CANCEL (wait4, pid, stat_loc, options, &usage32);
+
+      if (ret > 0)
+        rusage32_to_rusage64 (&usage32, usage);
+    }
+  else
+    ret = SYSCALL_CANCEL (wait4, pid, stat_loc, options, NULL);
 
   return ret;
 # endif
@@ -114,15 +118,19 @@ libc_hidden_def (__wait4_time64)
 pid_t
 __wait4 (pid_t pid, int *stat_loc, int options, struct rusage *usage)
 {
-  pid_t ret ;
-  struct __rusage64 usage64;
+  pid_t ret;
 
-  ret = __wait4_time64 (pid, stat_loc, options, &usage64);
+  if (usage != NULL)
+    {
+      struct __rusage64 usage64;
 
-  if (ret != 0)
-    return ret;
+      ret = __wait4_time64 (pid, stat_loc, options, &usage64);
 
-  rusage64_to_rusage (&usage64, usage);
+      if (ret > 0)
+        rusage64_to_rusage (&usage64, usage);
+    }
+  else
+    ret = __wait4_time64 (pid, stat_loc, options, NULL);
 
   return ret;
 }
-- 
2.26.0