Re: [PATCH] Handle jobserver file descriptors in btest.

["Martin Liška" <mliska@suse.cz>]

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On 10/21/21 20:15, Ian Lance Taylor wrote:
> On Thu, Oct 21, 2021 at 12:48 AM Martin Liška <mliska@suse.cz> wrote:
>>
>> The patch is about sensitive handling of file descriptors opened
>> by make's jobserver.
> 
> Thanks.  I think a better approach would be, at the start of main,
> fstat the descriptors up to 10 and record the ones for which fstat
> succeeds.  Then at the end of main only check the descriptors for
> which fstat failed earlier.

Sure, makes sense.

> 
> I can work on that at some point if you don't want to tackle it.

I've just done that in the attached patch.

Is it fine?
Thanks,
Martin

> 
> Ian
> 

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From ad52a33e10f76119867dbf0b6d5875378aa399ab Mon Sep 17 00:00:00 2001
From: Martin Liska <mliska@suse.cz>
Date: Fri, 22 Oct 2021 10:12:56 +0200
Subject: [PATCH] Handle jobserver file descriptors in btest.

	PR testsuite/102742

libbacktrace/ChangeLog:

	* btest.c (MIN_DESCRIPTOR): New.
	(MAX_DESCRIPTOR): Likewise.
	(check_available_files): Likewise.
	(check_open_files): Check only file descriptors that
	were not available at the entry.
	(main): Call check_available_files.
---
 libbacktrace/btest.c | 24 ++++++++++++++++++++----
 1 file changed, 20 insertions(+), 4 deletions(-)

diff --git a/libbacktrace/btest.c b/libbacktrace/btest.c
index 9f9c03babf3..7ef6d320497 100644
--- a/libbacktrace/btest.c
+++ b/libbacktrace/btest.c
@@ -38,6 +38,7 @@ POSSIBILITY OF SUCH DAMAGE.  */
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
+#include <sys/stat.h>
 
 #include "filenames.h"
 
@@ -458,16 +459,29 @@ test5 (void)
   return failures;
 }
 
+#define MIN_DESCRIPTOR 3
+#define MAX_DESCRIPTOR 10
+
+static int fstat_status[MAX_DESCRIPTOR];
+
+/* Check files that are available.  */
+
+static void
+check_available_files (void)
+{
+  struct stat s;
+  for (unsigned i = MIN_DESCRIPTOR; i < MAX_DESCRIPTOR; i++)
+    fstat_status[i] = fstat (i, &s);
+}
+
 /* Check that are no files left open.  */
 
 static void
 check_open_files (void)
 {
-  int i;
-
-  for (i = 3; i < 10; i++)
+  for (unsigned i = MIN_DESCRIPTOR; i < MAX_DESCRIPTOR; i++)
     {
-      if (close (i) == 0)
+      if (fstat_status[i] != 0 && close (i) == 0)
 	{
 	  fprintf (stderr,
 		   "ERROR: descriptor %d still open after tests complete\n",
@@ -482,6 +496,8 @@ check_open_files (void)
 int
 main (int argc ATTRIBUTE_UNUSED, char **argv)
 {
+  check_available_files ();
+
   state = backtrace_create_state (argv[0], BACKTRACE_SUPPORTS_THREADS,
 				  error_callback_create, NULL);
 
-- 
2.33.1