Eli Zaretskii wrote:
> Looking at your test program, I see that you generate the seconds file
> name without deleting the first one. When a file by the first
> generated name already exists, gen_tempname will indeed generate a
> different name. But in the scenario I described, Emacs creates one
> temporary file, uses it, then deletes it, and only after that creates
> another file.
I'm adding this scenario to the unit test. Still, the unit test succeeds
when run once on:
Linux, FreeBSD, NetBSD, OpenBSD, macOS, Solaris, Cygwin, native Windows.
Since this contradicts what you debugged on mingw, I ran the test 10000
times on native Windows. Result:
- on 32-bit mingw, no failure.
- on 64-bit mingw, around 30 failures (or around 10 failures with Paul's
newest patch). That is, a probability of ca. 0.3% of getting the same
file name as on the previous call.
Bruno
>From aa52cadc36fb1af0509dc3a4bce4ce73197ece68 Mon Sep 17 00:00:00 2001
From: Bruno Haible <br...@clisp.org>
Date: Tue, 16 Aug 2022 21:50:11 +0200
Subject: [PATCH] tempname: Add more tests.
Based on scenario described by Eli Zaretskii in
<https://lists.gnu.org/archive/html/bug-gnulib/2022-08/msg00043.html>.
* tests/test-tempname.c (main): Add another test.
* modules/tempname-tests (Status): Mark the test as unportable.
---
ChangeLog | 8 ++++++
modules/tempname-tests | 3 ++
tests/test-tempname.c | 65 ++++++++++++++++++++++++++++++------------
3 files changed, 58 insertions(+), 18 deletions(-)
diff --git a/ChangeLog b/ChangeLog
index eb96281591..de113ce081 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+2022-08-16 Bruno Haible <br...@clisp.org>
+
+ tempname: Add more tests.
+ Based on scenario described by Eli Zaretskii in
+ <https://lists.gnu.org/archive/html/bug-gnulib/2022-08/msg00043.html>.
+ * tests/test-tempname.c (main): Add another test.
+ * modules/tempname-tests (Status): Mark the test as unportable.
+
2022-08-16 Paul Eggert <egg...@cs.ucla.edu>
tempname: generate better names for MinGW Emacs
diff --git a/modules/tempname-tests b/modules/tempname-tests
index 384f98707b..adccd0d8e9 100644
--- a/modules/tempname-tests
+++ b/modules/tempname-tests
@@ -2,6 +2,9 @@ Files:
tests/test-tempname.c
tests/macros.h
+Status:
+unportable-test
+
Depends-on:
unlink
diff --git a/tests/test-tempname.c b/tests/test-tempname.c
index d463eec2b4..4a0ca65f2c 100644
--- a/tests/test-tempname.c
+++ b/tests/test-tempname.c
@@ -34,24 +34,53 @@ main ()
char filename1[18 + 1];
char filename2[18 + 1];
- strcpy (filename1, templ18);
- int fd1 = gen_tempname (filename1, strlen (".xyz"), 0, GT_FILE);
- ASSERT (fd1 >= 0);
-
- strcpy (filename2, templ18);
- int fd2 = gen_tempname (filename2, strlen (".xyz"), 0, GT_FILE);
- ASSERT (fd2 >= 0);
-
- /* With 6 'X' and a good pseudo-random number generator behind the scenes,
- the probability of getting the same file name twice in a row should be
- 1/62^6 < 1/10^10. */
- ASSERT (strcmp (filename1, filename2) != 0);
-
- /* Clean up. */
- close (fd1);
- close (fd2);
- unlink (filename1);
- unlink (filename2);
+ /* Case 1: The first file still exists while gen_tempname is called a second
+ time. */
+ {
+ strcpy (filename1, templ18);
+ int fd1 = gen_tempname (filename1, strlen (".xyz"), 0, GT_FILE);
+ ASSERT (fd1 >= 0);
+
+ strcpy (filename2, templ18);
+ int fd2 = gen_tempname (filename2, strlen (".xyz"), 0, GT_FILE);
+ ASSERT (fd2 >= 0);
+
+ /* gen_tempname arranges (via O_EXCL) to not return the name of an existing
+ file. */
+ ASSERT (strcmp (filename1, filename2) != 0);
+
+ /* Clean up. */
+ close (fd1);
+ close (fd2);
+ unlink (filename1);
+ unlink (filename2);
+ }
+
+ /* Case 2: The first file is deleted before gen_tempname is called a second
+ time. */
+ {
+ strcpy (filename1, templ18);
+ int fd1 = gen_tempname (filename1, strlen (".xyz"), 0, GT_FILE);
+ ASSERT (fd1 >= 0);
+
+ /* Clean up. */
+ close (fd1);
+ unlink (filename1);
+
+ strcpy (filename2, templ18);
+ int fd2 = gen_tempname (filename2, strlen (".xyz"), 0, GT_FILE);
+ ASSERT (fd2 >= 0);
+
+ /* With 6 'X' and a good pseudo-random number generator behind the scenes,
+ the probability of getting the same file name twice in a row should be
+ 1/62^6 < 1/10^10.
+ But on 64-bit native Windows, this probability is ca. 0.1% to 0.3%. */
+ ASSERT (strcmp (filename1, filename2) != 0);
+
+ /* Clean up. */
+ close (fd2);
+ unlink (filename2);
+ }
return 0;
}
--
2.34.1
