[PATCH] support: Set errno before testing it.

[Carlos O'Donell <carlos@redhat.com>]

DJ,

I looked over the whole tree, and I only found on occurance of
TEST_COMPARE (errno, 0); (and some variants) where we forgot to set
errno to zero.

Likewise in test-container.c we have an instance of strtol which doesn't
check error returns.

I've put these together in one patch to make testing easier. It fixes
both cases, the missing check, and the potentially broken check (depends
on what gets called before parse_int()).

OK for master?

8< --- 8< --- 8<
From 0adf117887d13925d9a00be1a0abd07ded6adfce Mon Sep 17 00:00:00 2001
From: Carlos O'Donell <carlos@redhat.com>
Date: Wed, 29 Apr 2020 16:31:29 -0400
Subject: [PATCH] support: Set errno before testing it.

In test-conainer we should set errno to 0 before calling chmod,
and check after with TEST_COMPARE.

In tst-support_capture_subprocess we should set errno to 0 before
checking it after the call to strtol.

Tested on x86_64.
---
 support/test-container.c                 | 2 ++
 support/tst-support_capture_subprocess.c | 4 +++-
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/support/test-container.c b/support/test-container.c
index 08d5195b7e..afc23db148 100644
--- a/support/test-container.c
+++ b/support/test-container.c
@@ -940,7 +940,9 @@ main (int argc, char **argv)
 	    else if (nt == 3 && strcmp (the_words[0], "chmod") == 0)
 	      {
 		long int m;
+		errno = 0;
 		m = strtol (the_words[1], NULL, 0);
+		TEST_COMPARE (errno, 0);
 		if (chmod (the_words[2], m) < 0)
 		    FAIL_EXIT1 ("chmod %s: %s\n",
 				the_words[2], strerror (errno));
diff --git a/support/tst-support_capture_subprocess.c b/support/tst-support_capture_subprocess.c
index 67bbc1e8ae..6094dba49e 100644
--- a/support/tst-support_capture_subprocess.c
+++ b/support/tst-support_capture_subprocess.c
@@ -133,7 +133,9 @@ static int
 parse_int (const char *str)
 {
   char *endptr;
-  long int ret = strtol (str, &endptr, 10);
+  long int ret;
+  errno = 0;
+  ret = strtol (str, &endptr, 10);
   TEST_COMPARE (errno, 0);
   TEST_VERIFY (ret >= 0 && ret <= INT_MAX);
   return ret;
-- 
2.21.1


-- 
Cheers,
Carlos.