Re: string length on Mac

I haven't used Fox in a long time, but I'm older than dirt. Please allow 
me to share a story that may or may not have anything to do with your 
problem.

Back in the days of DOS we had real compilers and real programmers, then 
we had Borland and those who used it. Borland "developers" spread like a 
pandemic throughout the industry. Since most of us were getting source 
code via BBS and long distance calls via modem, if you unzipped some 
source and the comments said it was developed using Borland, you just 
deleted everything. It was going to be faster to write it yourself than 
fix their "working, fully tested" code.

Borland, by default, automatically initialized everything. Real 
compilers did not. Some didn't even initialize stuff when compiling in 
debug mode. Borland users were just hacks and their stuff would crash 
all over the place when compiled with a real compiler. You could not 
port it to another platform to save your ass.

I took you on that picturesque journey down memory lane because what you 
describe is ___exactly___ the kind of Mystery Crash we would get back 
then. No, you aren't using Borland . . . but

1) Check your compilation switches, ALL of them, even the ones (if any) 
Fox turns on without telling you.

2) On the Linux platform, turn off any compiler switch that initializes 
anything for you so you can make it crash on Linux.

Once it crashes, if you are using Ubuntu or Linux Mint (or a Linux based 
on either) read this post:

https://www.logikalsolutions.com/wordpress/information-technology/core-dumps/

That will tell you how to enable core dumps. Then this post:

https://www.logikalsolutions.com/wordpress/information-technology/core-dumps-2/

Which will tell you how to use GDB within Emacs to debug a core dump.

I'm 99.999% certain you have one of two problems.

*Most likely:* as was eluded to in previous message, you somehow have a 
logic path that is attempting to utilize an uninitialized string. If you 
really are dying on length() you are dying on garbage that equates to a 
really big binary number for the length because it has "whatever" was 
left over in RAM.

*Second most likely:* You are using a pointer to "something else" that 
happens to point to where your string got allocated. You copied a big 
block of something there and now your string has garbage for the size 
and the length is larger than your physical memory.

*Third most likely:* You returned a string ___ that was locally 
allocated on the stack as a local variable___ via reference or address. 
Mac re-used that chunk of stack but the other two platforms hadn't 
gotten around to it yet.

PC-LINT used to be an awesome product for finding most of these 
problems. I assume it still is, but now it isn't a $350 tool you keep in 
the toolbox because they charge your first born child and 3 critical 
bodily organs for it.

CppCheck "might" help you but the "free" version is really neutered. A 
static analysis tool really could help you find some of these. Use the 
Wikipedia page at your own risk.

https://en.wikipedia.org/wiki/List_of_tools_for_static_code_analysis


On 4/16/2024 5:04 PM, Jeroen van der Zijp wrote:
> On Tue, 16 Apr 2024 17:20:41 -0400
> "John Selverian"<[email protected]>  wrote:
>
>> My program is crashing on start-up on the Mac.  It works fine on
>> Windows and Linux. I can't catch it in the debugger, it crashes
>> in FXString::length() in the fox lib. I have some long strings
>> (up to 2000 chars). Could this be the problem? Is there a length
>> limit for FXString?
> Length limit is, basically, MAX_INT (2**31-1).  Why does it
> crash?  I don't know.  I assume you've at least executed the
> FXString constructor?  FXString is essentially a pointer to
> a text buffer, preceded by the size of the string [there's
> an extra byte at the end, not accounted for in the length].
>
> An empty string is a special pointer, which is preceeded by
> a count of 0, and whose contents is a single end-of-string
> character ('\0').
>
>
>
>
>      -- JVZ
>
>
> _______________________________________________
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> [email protected]
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(630)-205-1593

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