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Newsgroups:	comp.os.msdos.djgpp
Date:	Mon, 29 Jul 2013 13:45:03 -0700 (PDT)
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Subject:	_CRT0_FLAG_NULLOK
From:	Georg Potthast <dosusb AT googlemail DOT com>
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To:	djgpp AT delorie DOT com
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Reply-To:	djgpp AT delorie DOT com

I got my program to work fine in real mode DOS now when I set this flag:

int _crt0_startup_flags = _CRT0_FLAG_NULLOK | _CRT0_FLAG_FILL_SBRK_MEMORY;

Without this line above it crashes when executing "atoi" in these lines:

const char* testchar = NULL;
int testint = atoi(testchar);
printf("testint:%d\n",testint);

I thought if I initialize a pointer to NULL I avoid problems like that. In my program I call a library function which returns NULL if it cannot read the requested value. I shortend this to testchar = NULL in the snippet above.

When I set the _crt0_startup_flags like above the variable testint gets the value zero. But is there a danger that the pointer could override memory, e.g. part of the operating system? Or why should I avoid _CRT0_FLAG_NULLOK ?

Georg

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