Changes to automatically enable large file support on some systems.

I believe this works on Linux (tested both on a system with large file
support and one without it), and it may work on Solaris 2.7.

The changes are twofold:

(1) The configure script now boldly tries to set the two symbols that
    are recommended (for Solaris and Linux), and then tries a test
    script that does some simple seeking without writing.

(2) The _portable_{fseek,ftell} functions are a little more systematic
    in how they try the different large file support options: first
    try fseeko/ftello, but only if off_t is large; then try
    fseek64/ftell64; then try hacking with fgetpos/fsetpos.

I'm keeping my fingers crossed.  The meaning of the
HAVE_LARGEFILE_SUPPORT macro is not at all clear.

I'll see if I can get it to work on Windows as well.

1 files changed, 20 insertions, 12 deletions

diff --git a/Objects/fileobject.c b/Objects/fileobject.c
index e18e2a2..f592e7a 100644
--- a/Objects/fileobject.c
+++ b/Objects/fileobject.c
@@ -208,11 +208,15 @@ file_close(PyFileObject *f)
 }
 
 
-/* An 8-byte off_t-like type */
-#if defined(HAVE_LARGEFILE_SUPPORT) && SIZEOF_OFF_T < 8 && SIZEOF_FPOS_T >= 8
+/* Our very own off_t-like type, 64-bit if possible */
+#if !defined(HAVE_LARGEFILE_SUPPORT)
+typedef off_t Py_off_t;
+#elif SIZEOF_OFF_T >= 8
+typedef off_t Py_off_t;
+#elif SIZEOF_FPOS_T >= 8
 typedef fpos_t Py_off_t;
 #else
-typedef off_t Py_off_t;
+#error "Large file support, but neither off_t nor fpos_t is large enough."
 #endif
 
 
@@ -221,13 +225,15 @@ typedef off_t Py_off_t;
 static int
 _portable_fseek(FILE *fp, Py_off_t offset, int whence)
 {
-#if defined(HAVE_FSEEKO)
+#if !defined(HAVE_LARGEFILE_SUPPORT)
+	return fseek(fp, offset, whence);
+#elif defined(HAVE_FSEEKO) && SIZEOF_OFF_T >= 8
 	return fseeko(fp, offset, whence);
 #elif defined(HAVE_FSEEK64)
 	return fseek64(fp, offset, whence);
 #elif defined(__BEOS__)
 	return _fseek(fp, offset, whence);
-#elif defined(HAVE_LARGEFILE_SUPPORT) && SIZEOF_FPOS_T >= 8
+#elif SIZEOF_FPOS_T >= 8
 	/* lacking a 64-bit capable fseek(), use a 64-bit capable fsetpos()
 	   and fgetpos() to implement fseek()*/
 	fpos_t pos;
@@ -245,7 +251,7 @@ _portable_fseek(FILE *fp, Py_off_t offset, int whence)
 	}
 	return fsetpos(fp, &offset);
 #else
-	return fseek(fp, offset, whence);
+#error "Large file support, but no way to fseek."
 #endif
 }
 
@@ -256,17 +262,19 @@ _portable_fseek(FILE *fp, Py_off_t offset, int whence)
 static Py_off_t
 _portable_ftell(FILE* fp)
 {
-#if SIZEOF_FPOS_T >= 8 && defined(HAVE_LARGEFILE_SUPPORT)
+#if !defined(HAVE_LARGEFILE_SUPPORT)
+	return ftell(fp);
+#elif defined(HAVE_FTELLO) && SIZEOF_OFF_T >= 8
+	return ftello(fp);
+#elif defined(HAVE_FTELL64)
+	return ftell64(fp);
+#elif SIZEOF_FPOS_T >= 8
 	fpos_t pos;
 	if (fgetpos(fp, &pos) != 0)
 		return -1;
 	return pos;
-#elif defined(HAVE_FTELLO) && defined(HAVE_LARGEFILE_SUPPORT)
-	return ftello(fp);
-#elif defined(HAVE_FTELL64) && defined(HAVE_LARGEFILE_SUPPORT)
-	return ftell64(fp);
 #else
-	return ftell(fp);
+#error "Large file support, but no way to ftell."
 #endif
 }