Re: Relocation patch for cygwin

[Bruno Haible]

Hi Chuck,

> Ping?

Thanks for the reminder. Three weeks ago, I concentrated on discussing the
support of UCS-4 characters (still working on that). I've added minor tweaks
(especially so as to avoid mixing the Win32 and the Cygwin approach), and
committed this:


2011-02-28  Corinna Vinschen  <address@hidden>  (tiny change)
            Charles Wilson  <address@hidden>  (tiny change)
            Bruno Haible  <address@hidden>  (tiny change)

        On Cygwin, use /proc file system instead of win32 API.
        * lib/relocatable.c: On Cygwin, use file names from /proc, rather than
        Win32 file names.
        (DllMain): Simplify by removing Cygwin specific code.
        (find_shared_library_fullname): Use Linux specific implementation also
        for Cygwin.
        (get_shared_library_fullname): Update accordingly.
        * lib/progreloc.c: On Cygwin, use file names from /proc, rather than
        Win32 file names.
        (find_executable): On Cygwin, use /proc, like on Linux. Remove previous
        Cygwin specific code.

--- lib/progreloc.c.orig        Mon Feb 28 23:09:10 2011
+++ lib/progreloc.c     Mon Feb 28 02:13:45 2011
@@ -34,11 +34,11 @@
 # include <mach-o/dyld.h>
 #endif
 
-#if defined _WIN32 || defined __WIN32__
+#if (defined _WIN32 || defined __WIN32__) && !defined __CYGWIN__
 # define WIN32_NATIVE
 #endif
 
-#if defined WIN32_NATIVE || defined __CYGWIN__
+#ifdef WIN32_NATIVE
 # define WIN32_LEAN_AND_MEAN
 # include <windows.h>
 #endif
@@ -72,8 +72,8 @@
    ISSLASH(C)           tests whether C is a directory separator character.
    IS_PATH_WITH_DIR(P)  tests whether P contains a directory specification.
  */
-#if defined _WIN32 || defined __WIN32__ || defined __CYGWIN__ || defined 
__EMX__ || defined __DJGPP__
-  /* Win32, Cygwin, OS/2, DOS */
+#if ((defined _WIN32 || defined __WIN32__) && !defined __CYGWIN__) || defined 
__EMX__ || defined __DJGPP__
+  /* Win32, OS/2, DOS */
 # define ISSLASH(C) ((C) == '/' || (C) == '\\')
 # define HAS_DEVICE(P) \
     ((((P)[0] >= 'A' && (P)[0] <= 'Z') || ((P)[0] >= 'a' && (P)[0] <= 'z')) \
@@ -102,7 +102,7 @@
 
 #if ENABLE_RELOCATABLE
 
-#ifdef __linux__
+#if defined __linux__ || defined __CYGWIN__
 /* File descriptor of the executable.
    (Only used to verify that we find the correct executable.)  */
 static int executable_fd = -1;
@@ -112,12 +112,13 @@
 static bool
 maybe_executable (const char *filename)
 {
-  /* Woe32 lacks the access() function, but Cygwin doesn't.  */
-#if !(defined WIN32_NATIVE && !defined __CYGWIN__)
+  /* Woe32 lacks the access() function.  */
+#if !defined WIN32_NATIVE
   if (access (filename, X_OK) < 0)
     return false;
+#endif
 
-# ifdef __linux__
+#if defined __linux__ || defined __CYGWIN__
   if (executable_fd >= 0)
     {
       /* If we already have an executable_fd, check that filename points to
@@ -135,7 +136,6 @@
             return false;
         }
     }
-# endif
 #endif
 
   return true;
@@ -148,7 +148,12 @@
 static char *
 find_executable (const char *argv0)
 {
-#if defined WIN32_NATIVE || defined __CYGWIN__
+#if defined WIN32_NATIVE
+  /* Native Win32 only.
+     On Cygwin, it is better to use the Cygwin provided /proc interface, than
+     to use native Win32 API and cygwin_conv_to_posix_path, because it supports
+     longer file names
+     (see <http://cygwin.com/ml/cygwin/2011-01/msg00410.html>).  */
   char location[MAX_PATH];
   int length = GetModuleFileName (NULL, location, sizeof (location));
   if (length < 0)
@@ -156,31 +161,8 @@
   if (!IS_PATH_WITH_DIR (location))
     /* Shouldn't happen.  */
     return NULL;
-  {
-# if defined __CYGWIN__
-    /* cygwin-1.5.13 (2005-03-01) or newer would also allow a Linux-like
-       implementation: readlink of "/proc/self/exe".  But using the
-       result of the Win32 system call is simpler and is consistent with the
-       code in relocatable.c.  */
-    /* On Cygwin, we need to convert paths coming from Win32 system calls
-       to the Unix-like slashified notation.  */
-    static char location_as_posix_path[2 * MAX_PATH];
-    /* There's no error return defined for cygwin_conv_to_posix_path.
-       See cygwin-api/func-cygwin-conv-to-posix-path.html.
-       Does it overflow the buffer of expected size MAX_PATH or does it
-       truncate the path?  I don't know.  Let's catch both.  */
-    cygwin_conv_to_posix_path (location, location_as_posix_path);
-    location_as_posix_path[MAX_PATH - 1] = '\0';
-    if (strlen (location_as_posix_path) >= MAX_PATH - 1)
-      /* A sign of buffer overflow or path truncation.  */
-      return NULL;
-    /* Call canonicalize_file_name, because Cygwin supports symbolic links.  */
-    return canonicalize_file_name (location_as_posix_path);
-# else
-    return xstrdup (location);
-# endif
-  }
-#else /* Unix && !Cygwin */
+  return xstrdup (location);
+#else /* Unix */
 # ifdef __linux__
   /* The executable is accessible as /proc/<pid>/exe.  In newer Linux
      versions, also as /proc/self/exe.  Linux >= 2.1 provides a symlink
@@ -206,6 +188,19 @@
     }
   }
 # endif
+# ifdef __CYGWIN__
+  /* The executable is accessible as /proc/<pid>/exe, at least in
+     Cygwin >= 1.5.  */
+  {
+    char *link;
+
+    link = xreadlink ("/proc/self/exe");
+    if (link != NULL)
+      return link;
+    if (executable_fd < 0)
+      executable_fd = open ("/proc/self/exe", O_EXEC, 0);
+  }
+# endif
 # if HAVE_MACH_O_DYLD_H && HAVE__NSGETEXECUTABLEPATH
   /* On MacOS X 10.2 or newer, the function
        int _NSGetExecutablePath (char *buf, uint32_t *bufsize);
--- lib/relocatable.c.orig      Mon Feb 28 23:09:10 2011
+++ lib/relocatable.c   Mon Feb 28 02:13:54 2011
@@ -43,7 +43,7 @@
 # include "xalloc.h"
 #endif
 
-#if defined _WIN32 || defined __WIN32__ || defined __CYGWIN__
+#if (defined _WIN32 || defined __WIN32__) && !defined __CYGWIN__
 # define WIN32_LEAN_AND_MEAN
 # include <windows.h>
 #endif
@@ -70,8 +70,8 @@
    ISSLASH(C)           tests whether C is a directory separator character.
    IS_PATH_WITH_DIR(P)  tests whether P contains a directory specification.
  */
-#if defined _WIN32 || defined __WIN32__ || defined __CYGWIN__ || defined 
__EMX__ || defined __DJGPP__
-  /* Win32, Cygwin, OS/2, DOS */
+#if ((defined _WIN32 || defined __WIN32__) && !defined __CYGWIN__) || defined 
__EMX__ || defined __DJGPP__
+  /* Win32, OS/2, DOS */
 # define ISSLASH(C) ((C) == '/' || (C) == '\\')
 # define HAS_DEVICE(P) \
     ((((P)[0] >= 'A' && (P)[0] <= 'Z') || ((P)[0] >= 'a' && (P)[0] <= 'z')) \
@@ -293,7 +293,12 @@
 /* Full pathname of shared library, or NULL.  */
 static char *shared_library_fullname;
 
-#if defined _WIN32 || defined __WIN32__ || defined __CYGWIN__
+#if (defined _WIN32 || defined __WIN32__) && !defined __CYGWIN__
+/* Native Win32 only.
+   On Cygwin, it is better to use the Cygwin provided /proc interface, than
+   to use native Win32 API and cygwin_conv_to_posix_path, because it supports
+   longer file names
+   (see <http://cygwin.com/ml/cygwin/2011-01/msg00410.html>).  */
 
 /* Determine the full pathname of the shared library when it is loaded.  */
 
@@ -315,38 +320,21 @@
         /* Shouldn't happen.  */
         return FALSE;
 
-      {
-#if defined __CYGWIN__
-        /* On Cygwin, we need to convert paths coming from Win32 system calls
-           to the Unix-like slashified notation.  */
-        static char location_as_posix_path[2 * MAX_PATH];
-        /* There's no error return defined for cygwin_conv_to_posix_path.
-           See cygwin-api/func-cygwin-conv-to-posix-path.html.
-           Does it overflow the buffer of expected size MAX_PATH or does it
-           truncate the path?  I don't know.  Let's catch both.  */
-        cygwin_conv_to_posix_path (location, location_as_posix_path);
-        location_as_posix_path[MAX_PATH - 1] = '\0';
-        if (strlen (location_as_posix_path) >= MAX_PATH - 1)
-          /* A sign of buffer overflow or path truncation.  */
-          return FALSE;
-        shared_library_fullname = strdup (location_as_posix_path);
-#else
-        shared_library_fullname = strdup (location);
-#endif
-      }
+      shared_library_fullname = strdup (location);
     }
 
   return TRUE;
 }
 
-#else /* Unix except Cygwin */
+#else /* Unix */
 
 static void
 find_shared_library_fullname ()
 {
-#if defined __linux__ && (__GLIBC__ >= 2 || defined __UCLIBC__)
+#if (defined __linux__ && (__GLIBC__ >= 2 || defined __UCLIBC__)) || defined 
__CYGWIN__
   /* Linux has /proc/self/maps. glibc 2 and uClibc have the getline()
-     function.  */
+     function.
+     Cygwin >= 1.5 has /proc/self/maps and the getline() function too.  */
   FILE *fp;
 
   /* Open the current process' maps file.  It describes one VMA per line.  */
@@ -391,7 +379,7 @@
 #endif
 }
 
-#endif /* (WIN32 or Cygwin) / (Unix except Cygwin) */
+#endif /* WIN32 / Unix */
 
 /* Return the full pathname of the current shared library.
    Return NULL if unknown.
@@ -399,7 +387,7 @@
 static char *
 get_shared_library_fullname ()
 {
-#if !(defined _WIN32 || defined __WIN32__ || defined __CYGWIN__)
+#if !((defined _WIN32 || defined __WIN32__) && !defined __CYGWIN__)
   static bool tried_find_shared_library_fullname;
   if (!tried_find_shared_library_fullname)
     {

-- 
In memoriam Olof Palme <http://en.wikipedia.org/wiki/Olof_Palme>