netbsd does not have KERN_PROC_PATHNAME but /proc/self/exe

[marcIhm]

Hi, thanx for your library !
(I am using it for my own project yabasic)

Found it is not working out of the box on netbsd but a simple modification helps.

Tested for netbsd 8.0

Thanx for merging (if you do …) !

[gpakosz]

Hello @marcIhm 👋

I don't really know NetBSD 😐

@jbeich Can you please chime in and tell us what you think about the proposed changes?

As far as I can tell, you made the judgment call to assume NetBSD has KERN_PROC_PATHNAME

Thanks in advance 🙏

[jbeich]

lldb KERN_PROC_PATHNAME source highligts the difference between FreeBSD and NetBSD. The correct order in name (the 1st argument) is also documented in sysctl(3) on FreeBSD and sysctl(7) on NetBSD.

@marcIhm, can you try the following instead?

diff --git a/src/whereami.c b/src/whereami.c
index 7441823..a43e975 100644
--- a/src/whereami.c
+++ b/src/whereami.c
@@ -576,17 +576,21 @@ int WAI_PREFIX(getExecutablePath)(char* out, int capacity, int* dirname_length)
   char buffer1[PATH_MAX];
   char buffer2[PATH_MAX];
   char* path = buffer1;
   char* resolved = NULL;
   int length = -1;
 
   for (;;)
   {
+#if defined(__NetBSD__)
+    int mib[4] = { CTL_KERN, KERN_PROC_ARGS, -1, KERN_PROC_PATHNAME };
+#else
     int mib[4] = { CTL_KERN, KERN_PROC, KERN_PROC_PATHNAME, -1 };
+#endif
     size_t size = sizeof(buffer1);
 
     if (sysctl(mib, (u_int)(sizeof(mib) / sizeof(mib[0])), path, &size, NULL, 0) != 0)
         break;
 
     resolved = realpath(path, buffer2);
     if (!resolved)
       break;

[jbeich]

NetBSD 6.x reached EOL a few months ago but NetBSD 7.x is still supported and lacks KERN_PROC_PATHNAME. Depending on the requirements NetBSD < 8.0 support can be left for downstream (e.g., PkgSrc) to deal with in order to avoid cruft when NetBSD 7.x reaches EOL (like Firefox, libuv, lldb do). Otherwise, you'd have to move <sys/sysctl.h> in order to check whether it defines KERN_PROC_PATHNAME e.g.,

diff --git a/src/whereami.c b/src/whereami.c
index 7441823..cda4e8d 100644
--- a/src/whereami.c
+++ b/src/whereami.c
@@ -7,16 +7,22 @@
 #if !defined(WHEREAMI_H)
 #include <whereami.h>
 #endif
 
 #ifdef __cplusplus
 extern "C" {
 #endif
 
+#if defined(__DragonFly__) || defined(__FreeBSD__) || \
+      defined(__FreeBSD_kernel__) || defined(__NetBSD__)
+#include <sys/types.h>
+#include <sys/sysctl.h>
+#endif
+
 #if !defined(WAI_MALLOC) || !defined(WAI_FREE) || !defined(WAI_REALLOC)
 #include <stdlib.h>
 #endif
 
 #if !defined(WAI_MALLOC)
 #define WAI_MALLOC(size) malloc(size)
 #endif
 
@@ -153,17 +159,17 @@ int WAI_PREFIX(getModulePath)(char* out, int capacity, int* dirname_length)
 #endif
   {
     length = WAI_PREFIX(getModulePath_)(module, out, capacity, dirname_length);
   }
 
   return length;
 }
 
-#elif defined(__linux__) || defined(__CYGWIN__) || defined(__sun)
+#elif defined(__linux__) || defined(__CYGWIN__) || defined(__sun) || (defined(__NetBSD__) && !defined(KERN_PROC_PATHNAME))
 
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #if defined(__linux__)
 #include <linux/limits.h>
 #else
 #include <limits.h>
@@ -555,38 +561,39 @@ int WAI_PREFIX(getModulePath)(char* out, int capacity, int* dirname_length)
     }
 
     break;
   }
 
   return length;
 }
 
-#elif defined(__DragonFly__) || defined(__FreeBSD__) || \
-      defined(__FreeBSD_kernel__) || defined(__NetBSD__)
+#elif defined(KERN_PROC_PATHNAME)
 
 #include <limits.h>
 #include <stdlib.h>
 #include <string.h>
-#include <sys/types.h>
-#include <sys/sysctl.h>
 #include <dlfcn.h>
 
 WAI_FUNCSPEC
 int WAI_PREFIX(getExecutablePath)(char* out, int capacity, int* dirname_length)
 {
   char buffer1[PATH_MAX];
   char buffer2[PATH_MAX];
   char* path = buffer1;
   char* resolved = NULL;
   int length = -1;
 
   for (;;)
   {
+#if defined(__NetBSD__)
+    int mib[4] = { CTL_KERN, KERN_PROC_ARGS, -1, KERN_PROC_PATHNAME };
+#else
     int mib[4] = { CTL_KERN, KERN_PROC, KERN_PROC_PATHNAME, -1 };
+#endif
     size_t size = sizeof(buffer1);
 
     if (sysctl(mib, (u_int)(sizeof(mib) / sizeof(mib[0])), path, &size, NULL, 0) != 0)
         break;
 
     resolved = realpath(path, buffer2);
     if (!resolved)
       break;

[krytarowski]

7.0 will get EOL probably soon as we are planning to release -9 earlier

[gpakosz]

Does inspecting /proc/self/exe work for NetBSD versions 6.0, 7.0 and 8.0?

[marcIhm]

The patch provided by Jan works for my netBSD 8 box like a charm; updated my pull request accordingly.

[gpakosz]

Well I vastly prefer your initial patch that inspects /proc/self/exe for all NetBSDs if it works for 6.0, 7.0 and 8.0.

This makes the code clearer than interspersing #ifdefs all over the place.

[marcIhm]

Reverted to the initial Version :-)

[krytarowski]

/proc is deprecated, please never use it except as a fallback for old versions of NetBSD (but at this point we can ignore them)

[marcIhm]

Okay, thanx to Kamils comment we are back at the Changes proposed by Jan. Seems like sometimes you just Need some ifdefs :-)
Hope this is Okay for you too Gregory !
Best regards
Marc

[gpakosz]

Time to iron things out!

My understanding is that the current code in master doesn't work for NetBSD at all:

• because there's no KERN_PROC_PATHNAME available for NetBSD < 8.0
• and because the arguments to sysctl() call are in wrong order

To avoid scattering the platform detection #ifdef dance all over the place, if you all agree, I suggest following @krytarowski's recommendation and not bother with NetBSD < 8.0.

If we really want to support NetBSD 7.0 or help packagers, we could alter line 161 to force the inspection of /self/proc/exe:

#elif defined(__linux__) || defined(__CYGWIN__) || defined(__sun) || defined(WAI_PROC_SELF_EXE)

What do you think?

If we all agree, for this PR to merge:

• Should @jbeich be made the author of the commit and @marcIhm the committer? 🤔
• Can you please make the PR a single commit and use a commit message that tells something like "fixed getExecutablePath() for NetBSD"? 🙏

Oh and happy new year 2019! 🎉

[marcIhm]

Yes, woule be great for me ! So it would be Jans first and simpler proposal without support for NetBSD 7 and earlier. (And Jan should be the author of Course !)

[gpakosz]

@marcIhm I squashed and pushed to your master branch, can you please confirm it's still working for you?

[marcIhm]

Just compiled and started yabasic on NetBSD 8: No Problems !

[gpakosz]

Thanks for improving whereami guys, appreciated 👍