Ken Cunningham wrote:
> That is not usually how this is done, although it might work and is suitably
> simple. The problem I suppose is the function definition can change somewhat
> over time.
>
> Usually, the SDK features automatically supply the weak import attribute
> features, based on your SDK and your deployment target.
>
> What was traditionally done (before the @available() compiler feature came
> out) is something like this, using as an example the function
> “pthread_threadid_np()” which is defined in the MacOSX 10.6 SDK and available
> in MacOSX version 10.6 and later.
>
> MAC_OS_X_VERSION_MAX_ALLOWED = the SDK you are building against
> MAC_OS_X_VERSION_MIN_REQUIRED = the minimum system you are willing to support
>
> ==========
> #if MAC_OS_X_VERSION_MAX_ALLOWED < 1060
> native_id = pthread_mach_thread_np(pthread_self());
> #elif MAC_OS_X_VERSION_MIN_REQUIRED < 1060
> if (&pthread_threadid_np) {
> (void) pthread_threadid_np(NULL, &native_id);
> } else {
> native_id = pthread_mach_thread_np(pthread_self());
> }
> #else
> (void) pthread_threadid_np(NULL, &native_id);
> #endif
> ========
Thanks; this code snippet confirms what I had guessed by looking
at other code.
> The function is automatically weak-linked by the SDK features.
That's not what I see with the 'proc_pidinfo' function. I need
to declare it with WEAK_IMPORT_ATTRIBUTE, so that the compiler
does not eliminate about the NULL test.
I'm thus applying this patch. The extra #if around the NULL test are
there, to disable compiler warnings
../../gllib/get_ppid_of.c:245:7: warning: comparison of function 'proc_pidinfo'
not equal to a null pointer is always true
[-Wtautological-pointer-compare]
if (proc_pidinfo != NULL) /* at runtime Mac OS X >= 10.5 ? */
^~~~~~~~~~~~ ~~~~
2021-12-21 Bruno Haible <br...@clisp.org>
get_ppid_of, get_progname_of: Fix runtime error on Mac OS X < 10.5.
Reported by Evan Miller <emmil...@gmail.com>
<https://lists.gnu.org/archive/html/bug-gnulib/2021-12/msg00081.html>.
* lib/get_ppid_of.c (proc_pidinfo): Declare with WEAK_IMPORT_ATTRIBUTE.
(get_ppid_of): Test whether the symbol declared weak evaluates to
non-NULL before invoking it.
* lib/get_progname_of (get_progname_of): Declare with
WEAK_IMPORT_ATTRIBUTE.
(get_ppid_of): Test whether the symbol declared weak evaluates to
non-NULL before invoking it.
diff --git a/lib/get_ppid_of.c b/lib/get_ppid_of.c
index dd4e38129..636dfa344 100644
--- a/lib/get_ppid_of.c
+++ b/lib/get_ppid_of.c
@@ -39,6 +39,12 @@
# include <AvailabilityMacros.h>
# if MAC_OS_X_VERSION_MAX_ALLOWED >= 1050
# include <libproc.h>
+# if MAC_OS_X_VERSION_MIN_REQUIRED < 1050
+/* Mac OS X versions < 10.5 don't have this function. Therefore declare it as
+ weak, in order to avoid a runtime error when the binaries are run on these
+ older versions. */
+extern int proc_pidinfo (int, int, uint64_t, void *, int)
WEAK_IMPORT_ATTRIBUTE;
+# endif
# endif
#endif
@@ -236,11 +242,16 @@ get_ppid_of (pid_t pid)
/* Mac OS X >= 10.7 has PROC_PIDT_SHORTBSDINFO. */
# if defined PROC_PIDT_SHORTBSDINFO
- struct proc_bsdshortinfo info;
+# if MAC_OS_X_VERSION_MIN_REQUIRED < 1050
+ if (proc_pidinfo != NULL) /* at runtime Mac OS X >= 10.5 ? */
+# endif
+ {
+ struct proc_bsdshortinfo info;
- if (proc_pidinfo (pid, PROC_PIDT_SHORTBSDINFO, 0, &info, sizeof (info))
- == sizeof (info))
- return info.pbsi_ppid;
+ if (proc_pidinfo (pid, PROC_PIDT_SHORTBSDINFO, 0, &info, sizeof (info))
+ == sizeof (info))
+ return info.pbsi_ppid;
+ }
# endif
# if MAC_OS_X_VERSION_MIN_REQUIRED < 1070
@@ -249,10 +260,15 @@ get_ppid_of (pid_t pid)
32-bit and 64-bit environments, and the kernel of Mac OS X 10.5 knows
only about the 32-bit 'struct proc_bsdinfo'. Fortunately all the info
we need is in the first part, which is the same in 32-bit and 64-bit. */
- struct proc_bsdinfo info;
+# if MAC_OS_X_VERSION_MIN_REQUIRED < 1050
+ if (proc_pidinfo != NULL) /* at runtime Mac OS X >= 10.5 ? */
+# endif
+ {
+ struct proc_bsdinfo info;
- if (proc_pidinfo (pid, PROC_PIDTBSDINFO, 0, &info, 128) == 128)
- return info.pbi_ppid;
+ if (proc_pidinfo (pid, PROC_PIDTBSDINFO, 0, &info, 128) == 128)
+ return info.pbi_ppid;
+ }
# endif
# endif
diff --git a/lib/get_progname_of.c b/lib/get_progname_of.c
index bdda3c60d..a5b99c038 100644
--- a/lib/get_progname_of.c
+++ b/lib/get_progname_of.c
@@ -47,6 +47,12 @@
# include <AvailabilityMacros.h>
# if MAC_OS_X_VERSION_MAX_ALLOWED >= 1050
# include <libproc.h>
+# if MAC_OS_X_VERSION_MIN_REQUIRED < 1050
+/* Mac OS X versions < 10.5 don't have this function. Therefore declare it as
+ weak, in order to avoid a runtime error when the binaries are run on these
+ older versions. */
+extern int proc_pidinfo (int, int, uint64_t, void *, int)
WEAK_IMPORT_ATTRIBUTE;
+# endif
# endif
#endif
@@ -276,11 +282,16 @@ get_progname_of (pid_t pid)
/* Mac OS X >= 10.7 has PROC_PIDT_SHORTBSDINFO. */
# if defined PROC_PIDT_SHORTBSDINFO
- struct proc_bsdshortinfo info;
+# if MAC_OS_X_VERSION_MIN_REQUIRED < 1050
+ if (proc_pidinfo != NULL) /* at runtime Mac OS X >= 10.5 ? */
+# endif
+ {
+ struct proc_bsdshortinfo info;
- if (proc_pidinfo (pid, PROC_PIDT_SHORTBSDINFO, 0, &info, sizeof (info))
- == sizeof (info))
- return strdup (info.pbsi_comm);
+ if (proc_pidinfo (pid, PROC_PIDT_SHORTBSDINFO, 0, &info, sizeof (info))
+ == sizeof (info))
+ return strdup (info.pbsi_comm);
+ }
# endif
# if MAC_OS_X_VERSION_MIN_REQUIRED < 1070
@@ -289,10 +300,15 @@ get_progname_of (pid_t pid)
32-bit and 64-bit environments, and the kernel of Mac OS X 10.5 knows
only about the 32-bit 'struct proc_bsdinfo'. Fortunately all the info
we need is in the first part, which is the same in 32-bit and 64-bit. */
- struct proc_bsdinfo info;
+# if MAC_OS_X_VERSION_MIN_REQUIRED < 1050
+ if (proc_pidinfo != NULL) /* at runtime Mac OS X >= 10.5 ? */
+# endif
+ {
+ struct proc_bsdinfo info;
- if (proc_pidinfo (pid, PROC_PIDTBSDINFO, 0, &info, 128) == 128)
- return strdup (info.pbi_comm);
+ if (proc_pidinfo (pid, PROC_PIDTBSDINFO, 0, &info, 128) == 128)
+ return strdup (info.pbi_comm);
+ }
# endif
# endif
