open, openat: Really support O_CLOEXEC.

* lib/open.c (open): When have_cloexec is still undecided, do pass a
O_CLOEXEC flag to orig_open.
* lib/openat.c (rpl_openat): When have_cloexec is still undecided, do
pass a O_CLOEXEC flag to orig_openat.
* tests/test-open.h (test_open): Verify that O_CLOEXEC is honoured.
* modules/open-tests (Depends-on): Add fcntl.
* modules/openat-tests (Depends-on): Likewise.
* modules/fcntl-safer-tests (Depends-on): Likewise.

7 files changed, 37 insertions, 2 deletions

diff --git a/ChangeLog b/ChangeLog
index 4dd90f83a1..ae9fae472f 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,17 @@
 2020-05-24  Bruno Haible  <bruno@clisp.org>
 
+	open, openat: Really support O_CLOEXEC.
+	* lib/open.c (open): When have_cloexec is still undecided, do pass a
+	O_CLOEXEC flag to orig_open.
+	* lib/openat.c (rpl_openat): When have_cloexec is still undecided, do
+	pass a O_CLOEXEC flag to orig_openat.
+	* tests/test-open.h (test_open): Verify that O_CLOEXEC is honoured.
+	* modules/open-tests (Depends-on): Add fcntl.
+	* modules/openat-tests (Depends-on): Likewise.
+	* modules/fcntl-safer-tests (Depends-on): Likewise.
+
+2020-05-24  Bruno Haible  <bruno@clisp.org>
+
 	fopen: Fix the trailing slash workaround.
 	* lib/fopen.c (rpl_fopen): Parse the mode string. Recognize "r+" as a
 	write access. Pass the right flags to open().
diff --git a/lib/open.c b/lib/open.c
index bb180fde29..751b42d7dc 100644
--- a/lib/open.c
+++ b/lib/open.c
@@ -124,7 +124,7 @@ open (const char *filename, int flags, ...)
 #endif
 
   fd = orig_open (filename,
-                  flags & ~(have_cloexec <= 0 ? O_CLOEXEC : 0), mode);
+                  flags & ~(have_cloexec < 0 ? O_CLOEXEC : 0), mode);
 
   if (flags & O_CLOEXEC)
     {
diff --git a/lib/openat.c b/lib/openat.c
index 974f1a8b3b..fbe1d2e6e6 100644
--- a/lib/openat.c
+++ b/lib/openat.c
@@ -114,7 +114,7 @@ rpl_openat (int dfd, char const *filename, int flags, ...)
 # endif
 
   fd = orig_openat (dfd, filename,
-                    flags & ~(have_cloexec <= 0 ? O_CLOEXEC : 0), mode);
+                    flags & ~(have_cloexec < 0 ? O_CLOEXEC : 0), mode);
 
   if (flags & O_CLOEXEC)
     {
diff --git a/modules/fcntl-safer-tests b/modules/fcntl-safer-tests
index cb35aed252..b967c8aa78 100644
--- a/modules/fcntl-safer-tests
+++ b/modules/fcntl-safer-tests
@@ -5,6 +5,7 @@ tests/macros.h
 
 Depends-on:
 stdbool
+fcntl
 symlink
 
 configure.ac:
diff --git a/modules/open-tests b/modules/open-tests
index 5bc4e0f885..b2b6710e5c 100644
--- a/modules/open-tests
+++ b/modules/open-tests
@@ -6,6 +6,7 @@ tests/macros.h
 
 Depends-on:
 stdbool
+fcntl
 symlink
 
 configure.ac:
diff --git a/modules/openat-tests b/modules/openat-tests
index 0b7370d6f2..c4a72f5fb8 100644
--- a/modules/openat-tests
+++ b/modules/openat-tests
@@ -5,6 +5,7 @@ tests/signature.h
 tests/macros.h
 
 Depends-on:
+fcntl
 symlink
 
 configure.ac:
diff --git a/tests/test-open.h b/tests/test-open.h
index c57054f747..862c8dfa53 100644
--- a/tests/test-open.h
+++ b/tests/test-open.h
@@ -88,6 +88,26 @@ test_open (int (*func) (char const *, int, ...), bool print)
   ASSERT (0 <= fd);
   ASSERT (close (fd) == 0);
 
+  /* O_CLOEXEC must be honoured.  */
+  if (O_CLOEXEC)
+    {
+      /* Since the O_CLOEXEC handling goes through a special code path at its
+         first invocation, test it twice.  */
+      int i;
+
+      for (i = 0; i < 2; i++)
+        {
+          int flags;
+
+          fd = func (BASE "file", O_CLOEXEC | O_RDONLY);
+          ASSERT (0 <= fd);
+          flags = fcntl (fd, F_GETFD);
+          ASSERT (flags >= 0);
+          ASSERT ((flags & FD_CLOEXEC) != 0);
+          ASSERT (close (fd) == 0);
+        }
+    }
+
   /* Symlink handling, where supported.  */
   if (symlink (BASE "file", BASE "link") != 0)
     {