POV-Ray : Newsgroups : povray.beta-test : v3.8 beta 2 seg fault. 32 bit raspbian os on 64 bit pi 4 hardware. : v3.8 beta 2 seg fault. 32 bit raspbian os on 64 bit pi 4 hardware. Server Time
24 Sep 2021 06:06:25 EDT (-0400)
  v3.8 beta 2 seg fault. 32 bit raspbian os on 64 bit pi 4 hardware.  
From: William F Pokorny
Date: 26 Aug 2021 15:19:44
Message: <6127e950$1@news.povray.org>
While I was doing a long overdue disk back up for my main machine, I 
decided to try a compile of the beta 2 release on my raspberry pi 4 4GB- 
which happened to be running the more common 32bit rasbian os(1).

The configure and compile went mostly OK, except I had trouble getting a 
tiff development library installed - for reasons not related to POV-Ray 
and which I've not sorted. There are a lot of extra 'notes' from the 
compiler over the usual warnings which can probably be turned off, but I 
didn't chase these.

We get an almost immediate segfault trying to run even stuff like povray 
--help which comes from vfe/vfesession.cpp. I expect others would follow 
should one get to where we start to render anything.

We have four unix flavor configuration files in:




All have nearly identical set up code that I've changed - in povr - to:

#if (0)  // Use simpler c++11 method TODO remove 0 if no issues
#if defined(_POSIX_V6_LPBIG_OFFBIG) || defined(_POSIX_V6_LP64_OFF64)
     // Below NOT true 32 raspbian os on 64bit raspberry pi 4 hardware.
     // long is at least 64 bits.
     #define POV_LONG long
#elif defined(_POSIX_V6_ILP32_OFFBIG) || defined(_POSIX_V6_ILP32_OFF32)
     // long is 32 bits.
     #define POV_LONG long long
     // Unable to detect long size at compile-time, assuming less than 
64 bits.
     #define POV_LONG long long

#define POV_ULONG unsigned POV_LONG

#else   //----------------------------

// C++11 required so we can just set macros directly.
#define POV_LONG  std::int_least64_t
#define POV_ULONG std::uint_least64_t
#endif  // Use simpler c++11 method

(1) - There is now a 64bit raspbian os mostly aimed at the newer 8GB 
models and there has been for quite a while 64bit Ubuntu versions for 
the raspberry pi 4. Not everyone with a raspberry pi will hit this 
issue, but many with a raspberry pi 4 will.

The issue can be guessed at from the code comments; It turns out that 
first test can be true and the 'long int' not be at 64 bits as the code 
comment states. The C++11 standard guarantees 'long long int' is at 
least 64bits, but 'long int' can be only 32 bits and this we get with 
the raspbian 32 bit os.

Aside: We have code since the move to c++11 taking POV_LONG and 
POV_ULONG to always be 64 bits - the bit in vfesession.cpp is just the 
first tripped upon where this not true. The code there has a hard LL 
literal assuming long long int is 64 bits.

Bill P.

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