--- a/ChangeLog	Tue Feb 19 21:38:53 2019 +0100
+++ b/ChangeLog	Tue Feb 19 21:42:54 2019 +0100
@@ -1,3 +1,11 @@
+2019-02-19  Bruno Haible  <bruno@clisp.org>
+
+	progreloc: Speed up executable lookup on various platforms.
+	* lib/progreloc.c: Include <errno.h>.
+	(safe_read, full_read): New functions.
+	(find_executable): On GNU/kFreeBSD, FreeBSD, DragonFly, NetBSD, Solaris,
+	prefer the information from the /proc file system to a PATH search.
+
 2019-02-19  Bruno Haible  <bruno@clisp.org>
 
 	progreloc: Simplify code for Android.

--- a/lib/progreloc.c	Tue Feb 19 21:38:53 2019 +0100
+++ b/lib/progreloc.c	Tue Feb 19 21:42:54 2019 +0100
@@ -22,6 +22,7 @@
 /* Specification.  */
 #include "progname.h"
 
+#include <errno.h>
 #include <stdbool.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -102,6 +103,48 @@
 
 #if ENABLE_RELOCATABLE
 
+#ifdef __sun
+
+/* Helper function, from gnulib module 'safe-read'.  */
+static size_t
+safe_read (int fd, void *buf, size_t count)
+{
+  for (;;)
+    {
+      ssize_t result = read (fd, buf, count);
+
+      if (0 <= result || errno != EINTR)
+        return result;
+    }
+}
+
+/* Helper function, from gnulib module 'full-read'.  */
+static size_t
+full_read (int fd, void *buf, size_t count)
+{
+  size_t total = 0;
+  const char *ptr = (const char *) buf;
+
+  while (count > 0)
+    {
+      size_t n = safe_read (fd, ptr, count);
+      if (n == (size_t) -1)
+        break;
+      if (n == 0)
+        {
+          errno = 0;
+          break;
+        }
+      total += n;
+      ptr += n;
+      count -= n;
+    }
+
+  return total;
+}
+
+#endif
+
 #if defined __linux__ || defined __CYGWIN__
 /* File descriptor of the executable.
    (Only used to verify that we find the correct executable.)  */
@@ -205,7 +248,9 @@
     }
   }
 # endif
-# if defined __ANDROID__
+# if defined __ANDROID__ || defined __FreeBSD_kernel__
+  /* On Android and GNU/kFreeBSD, the executable is accessible as
+     /proc/<pid>/exe and /proc/self/exe.  */
   {
     char *link;
 
@@ -214,7 +259,52 @@
       return link;
   }
 # endif
-# ifdef __CYGWIN__
+# if defined __FreeBSD__ || defined __DragonFly__
+  /* In FreeBSD >= 5.0, the executable is accessible as /proc/<pid>/file and
+     /proc/curproc/file.  */
+  {
+    char *link;
+
+    link = xreadlink ("/proc/curproc/file");
+    if (link != NULL)
+      {
+        if (strcmp (link, "unknown") != 0)
+          return link;
+        free (link);
+      }
+  }
+# endif
+# if defined __NetBSD__
+  /* In NetBSD >= 4.0, the executable is accessible as /proc/<pid>/exe and
+     /proc/curproc/exe.  */
+  {
+    char *link;
+
+    link = xreadlink ("/proc/curproc/exe");
+    if (link != NULL)
+      return link;
+  }
+# endif
+# if defined __sun
+  /* On Solaris >= 11.4, /proc/<pid>/execname and /proc/self/execname contains
+     the name of the executable, either as an absolute file name or relative to
+     the current directory.  */
+  {
+    char namebuf[4096];
+    int fd = open ("/proc/self/execname", O_RDONLY, 0);
+    if (fd >= 0)
+      {
+        size_t len = full_read (fd, namebuf, sizeof (namebuf));
+        close (fd);
+        if (len > 0 && len < sizeof (namebuf))
+          {
+            namebuf[len] = '\0';
+            return canonicalize_file_name (namebuf);
+          }
+      }
+  }
+# endif
+# if defined __CYGWIN__
   /* The executable is accessible as /proc/<pid>/exe, at least in
      Cygwin >= 1.5.  */
   {