Re: [PATCH] Don't look for kernel version if not running on linux

[Mark Wielaard <mark@klomp.org>]

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On Tue, May 02, 2017 at 12:17:24PM +0200, Ulf Hermann wrote:
> > You can get uname() on Windows through gnulib, but at the cost at
> > linking to additional windows DLLs. It calls gethostname and for that
> > we need to link against ws2_32.dll. That's an unreasonable dependency
> > for getting something we cannot use anyway. I suggest we just set
> > errno to ENOTSUP then.
> 
> I should clarify this a bit. We only use uname() to obtain the kernel
> version and we only use the kernel version to search for directories
> containing kernel modules. The only operating system where this makes sense
> is linux as we cannot handle anything but linux kernel modules there.
> Therefore there is no point in retrieving the kernel version on any other
> OS.

Agreed. So committed as attached.

Thanks,

Mark

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From e88787f9cd2af5be00aa6f53320cf85f7c08f1f2 Mon Sep 17 00:00:00 2001
From: Ulf Hermann <ulf.hermann@qt.io>
Date: Thu, 20 Apr 2017 16:08:48 +0200
Subject: [PATCH] Don't look for kernel version if not running on linux

We don't want to use it, even if it exists.

Signed-off-by: Ulf Hermann <ulf.hermann@qt.io>
Signed-off-by: Mark Wielaard <mark@klomp.org>
---
 libdwfl/ChangeLog              | 6 ++++++
 libdwfl/linux-kernel-modules.c | 7 +++++++
 2 files changed, 13 insertions(+)

diff --git a/libdwfl/ChangeLog b/libdwfl/ChangeLog
index 1fc9da6..859b2ff 100644
--- a/libdwfl/ChangeLog
+++ b/libdwfl/ChangeLog
@@ -1,4 +1,10 @@
 2017-04-20  Ulf Hermann  <ulf.hermann@qt.io>
+	    Mark Wielaard  <mark@klomp.org>
+
+	* linux-kernel-modules.c: Always return NULL from kernel_release() on
+	non-linux systems and set errno to ENOTSUP.
+
+2017-04-20  Ulf Hermann  <ulf.hermann@qt.io>
 
 	* libdwflP.h: Don't include config.h.
 	* argp-std.c: Include config.h.
diff --git a/libdwfl/linux-kernel-modules.c b/libdwfl/linux-kernel-modules.c
index 893110a..9d0fef2 100644
--- a/libdwfl/linux-kernel-modules.c
+++ b/libdwfl/linux-kernel-modules.c
@@ -156,11 +156,18 @@ try_kernel_name (Dwfl *dwfl, char **fname, bool try_debug)
 static inline const char *
 kernel_release (void)
 {
+#ifdef __linux__
   /* Cache the `uname -r` string we'll use.  */
   static struct utsname utsname;
   if (utsname.release[0] == '\0' && uname (&utsname) != 0)
     return NULL;
   return utsname.release;
+#else
+  /* Used for finding the running linux kernel, which isn't supported
+     on non-linux kernel systems.  */
+  errno = ENOTSUP;
+  return NULL;
+#endif
 }
 
 static int
-- 
2.9.3