[sldev] OpenJPEG MAX_PATH issue

[David Fries]

Give it a read through and let me know what you think?

Summary: MAX_PATH or PATH_MAX, and how to make everything see the same
size?  My suggestion?  See if OpenJPEG can just do,
#define OPJ_PATH_LEN 4096
and use that in their data structures.  (patch attached against
openjpeg_v1_1.tar.gz)

I was having a problem that was causing the open source version of the
Second Life viewer to crash with the OpenJPEG library.  I tracked it
down to openjpeg.h and the opj_cparameters structure.  There are three
character arrays in that data structure that are of size MAX_PATH.
openjpeg.h contains a check to define MAX_PATH to 260 if it isn't
defined.  When I compiled OpenJPEG it wasn't defined.  Second Life on
the other hand defines it, to some other size, so that
LLImageJ2COJ::encodeImpl creates a structure that is bigger in size
and passes a pointer for OpenJPEG to initialize.  OpenJPEG's library
has a different and smaller layout for the data variables in that
structure.  Thus encodeImpl reads garbage when it goes to process what
OpenJPEG initialized and crashes.

I started looking through the header files on my system to see what
has PATH_MAX listed in it, no standard system libraries define it or
use it.  Here are the results.

/usr/include/boost/regex/v4/fileiter.hpp
	boost regular expression library, defines MAX_PATH to 256 if
	it isn't already defined.
/usr/include/lcms.h
	Color management library, defines MAX_PATH to 256 without even
	checking to see if it was previously defined.
/usr/include/X11/Xos.h
	X11 core library, doesn't even check just
	#define MAX_PATH _POSIX_PATH_MAX
	(and then doesn't even use it).

On the other hand there are 20 files that use PATH_MAX and it is
mentioned in various man pages.

/usr/include/limits.h is the place to pick up PATH_MAX
/usr/include/linux/limits.h (which shouldn't be included directly)
#define PATH_MAX        4096	/* # chars in a path name including nul */

Then there is one that will change the size of PATH_MAX on windows.
/usr/include/X11/Xwindows.h
#if defined(WIN32) && (!defined(PATH_MAX) || PATH_MAX < 1024)
#undef PATH_MAX
#define PATH_MAX 1024
#endif

Looking around there are a few different sizes for PATH_MAX
/usr/include/linux/limits.h:#define PATH_MAX        4096
/usr/include/X11/Xwindows.h:#define PATH_MAX 1024
/usr/include/X11/InitialI.h:#define PATH_MAX 512

I think this is telling,

/usr/include/postgresql/pg_config_manual.h
/*
 * MAXPGPATH: standard size of a pathname buffer in PostgreSQL (hence,
 * maximum usable pathname length is one less).
 *
 * We'd use a standard system header symbol for this, if there weren't
 * so many to choose from: MAXPATHLEN, MAX_PATH, PATH_MAX are all
 * defined by different "standards", and often have different values
 * on the same platform!  So we just punt and use a reasonably
 * generous setting here.
 */
#define MAXPGPATH               1024

-- 
David Fries <david at fries.net>
http://fries.net/~david/ (PGP encryption key available)
-------------- next part --------------
--- ./OpenJPEG/libopenjpeg/openjpeg.h	2006-12-04 08:59:33.000000000 -0600
+++ ./DebugOpenJPEG/libopenjpeg/openjpeg.h	2007-01-20 16:14:06.000000000 -0600
@@ -89,9 +89,8 @@
 ==========================================================
 */
 
-#ifndef MAX_PATH
-#define MAX_PATH 260	/**< Maximum allowed size for filenames */
-#endif /* MAX_PATH */
+
+#define OPG_PATH_LEN 4096
 
 #define J2K_MAXRLVLS 33					/**< Number of maximum resolution level authorized */
 #define J2K_MAXBANDS (3*J2K_MAXRLVLS-2)	/**< Number of maximum sub-band linked to number of resolution level */
@@ -255,13 +254,13 @@
 	/**@name command line encoder parameters (not used inside the library) */
 	/*@{*/
 	/** input file name */
-	char infile[MAX_PATH];
+	char infile[OPG_PATH_LEN];
 	/** output file name */
-	char outfile[MAX_PATH];
+	char outfile[OPG_PATH_LEN];
 	/** creation of an index file, default to 0 (false) */
 	int index_on;
 	/** index file name */
-	char index[MAX_PATH];
+	char index[OPG_PATH_LEN];
 	/** subimage encoding: origin image offset in x direction */
 	int image_offset_x0;
 	/** subimage encoding: origin image offset in y direction */
@@ -335,9 +334,9 @@
 	/**@name command line encoder parameters (not used inside the library) */
 	/*@{*/
 	/** input file name */
-	char infile[MAX_PATH];
+	char infile[OPG_PATH_LEN];
 	/** output file name */
-	char outfile[MAX_PATH];
+	char outfile[OPG_PATH_LEN];
 	/** input file format 0: J2K, 1: JP2, 2: JPT */
 	int decod_format;
 	/** output file format 0: PGX, 1: PxM, 2: BMP */