patch [#25490] Fix for [#22096] Blender tries to open non-blend file

from Alexander Kuznetsov (alexk) with edits.

From the report:
Blender assumed that all files are .blend as retval = 0;

Now retval is initialized as file cannot be open (-1) for gzopen fail and directory case
retval = -2; is defined for not supported formats
This must be assigned before #ifdef WITH_PYTHON because this part can be missing
Finally retval = 0; if it is a .blend file

---
also made other edits.

- exotic.c's blend header checking was sloppy, didn't check data was actually read, only checked first 4 bytes and had a check for "blend.gz" extension which is unnecessary.
- use defines to help readability for BKE_read_exotic & BKE_read_file return values.
- no need to check for a NULL pointer before calling BKE_reportf(). (will just print to the console)
- print better reports when the file fails to load.

1 files changed, 0 insertions, 2 deletions

diff --git a/source/blender/blenkernel/BKE_utildefines.h b/source/blender/blenkernel/BKE_utildefines.h
index 605a50e078b..f152ff16afb 100644
--- a/source/blender/blenkernel/BKE_utildefines.h
+++ b/source/blender/blenkernel/BKE_utildefines.h
@@ -203,8 +203,6 @@ do { \
 
 #define ID_NEW(a)		if( (a) && (a)->id.newid ) (a)= (void *)(a)->id.newid
 
-#define FORM MAKE_ID('F','O','R','M')
-
 #define BLEN MAKE_ID('B','L','E','N')
 #define DER_ MAKE_ID('D','E','R','_')
 #define V100 MAKE_ID('V','1','0','0')