Libguestfs - Sep 2015 - [PATCH] daemon: initrd: print return value from failing process

If either zcat or cpio fails when spawned in initrd-list, pclose will
return the actual return value of it, but reply_with_perror still uses
errno regardless; thus, the reported error is:

  libguestfs: error: initrd_list: pclose: Success

which is not much helpful.

Instead, when pclose returns > 0, extract the actual return value of the
subprocess, and print that. Thus now we get for example:

  libguestfs: error: initrd_list: pclose: command failed with return code 1
---
 daemon/initrd.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/daemon/initrd.c b/daemon/initrd.c
index ac14826..c9fc2dd 100644
--- a/daemon/initrd.c
+++ b/daemon/initrd.c
@@ -43,6 +43,7 @@ do_initrd_list (const char *path)
   CLEANUP_FREE char *filename = NULL;
   size_t allocsize;
   ssize_t len;
+  int ret;
 
   /* "zcat /sysroot/<path> | cpio --quiet -it", but path must
be quoted. */
   if (asprintf_nowarn (&cmd, "%s %R | %s --quiet -it", str_zcat,
path, str_cpio) == -1) {
@@ -74,8 +75,15 @@ do_initrd_list (const char *path)
     return NULL;
   }
 
-  if (pclose (fp) != 0) {
-    reply_with_perror ("pclose");
+  ret = pclose (fp);
+  if (ret != 0) {
+    if (ret == -1)
+      reply_with_perror ("pclose");
+    else {
+      if (WEXITSTATUS (ret) != 0)
+        ret = WEXITSTATUS (ret);
+      reply_with_error ("pclose: command failed with return code %d",
ret);
+    }
     free_stringslen (filenames.argv, filenames.size);
     return NULL;
   }
-- 
2.1.0

On Tue, Sep 15, 2015 at 10:20:11AM +0200, Pino Toscano
wrote:
> If either zcat or cpio fails when spawned in initrd-list, pclose will
> return the actual return value of it, but reply_with_perror still uses
> errno regardless; thus, the reported error is:
> 
>   libguestfs: error: initrd_list: pclose: Success
> 
> which is not much helpful.
> 
> Instead, when pclose returns > 0, extract the actual return value of the
> subprocess, and print that. Thus now we get for example:
> 
>   libguestfs: error: initrd_list: pclose: command failed with return code 1
> ---
>  daemon/initrd.c | 12 ++++++++++--
>  1 file changed, 10 insertions(+), 2 deletions(-)
> 
> diff --git a/daemon/initrd.c b/daemon/initrd.c
> index ac14826..c9fc2dd 100644
> --- a/daemon/initrd.c
> +++ b/daemon/initrd.c
> @@ -43,6 +43,7 @@ do_initrd_list (const char *path)
>    CLEANUP_FREE char *filename = NULL;
>    size_t allocsize;
>    ssize_t len;
> +  int ret;
>  
>    /* "zcat /sysroot/<path> | cpio --quiet -it", but path
must be quoted. */
>    if (asprintf_nowarn (&cmd, "%s %R | %s --quiet -it",
str_zcat, path, str_cpio) == -1) {
> @@ -74,8 +75,15 @@ do_initrd_list (const char *path)
>      return NULL;
>    }
>  
> -  if (pclose (fp) != 0) {
> -    reply_with_perror ("pclose");
> +  ret = pclose (fp);
> +  if (ret != 0) {
> +    if (ret == -1)
> +      reply_with_perror ("pclose");
> +    else {
> +      if (WEXITSTATUS (ret) != 0)
> +        ret = WEXITSTATUS (ret);
> +      reply_with_error ("pclose: command failed with return code
%d", ret);
> +    }
>      free_stringslen (filenames.argv, filenames.size);
>      return NULL;
>    }
ACK.

Rich.

-- 
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