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Full Discussion: Newline in ANSI-C standard functions
Top Forums Programming Newline in ANSI-C standard functions Post 303020120 by jim mcnamara on Friday 13th of July 2018 08:50:12 PM
Old 07-13-2018
You are depending on the existence of a terminating NUL. You write 128 total and leave no room in the shorter string str1. You leave no terminating NUL. strcpy printf and lots of other functions depend on the existence of correclty terminated strings. Your sis not.

memset does not care where the end of a string is. Make str1[129], then write less than a total of 129 to str1. Or write fewer characters total to str1.

You are getting undefined behavior. That means I cannot know what your environment is doing or has done. You cannot ever know either. It could crash the program, compose a poem, or order a pizza.


I am guessing. If str1 precedes str2 in memory and each one is word-aligned, then the last character you write to str1[128] effectively cause the end of of str1 to be the actual end of str2. As far as strcpy, printf and so on are concerned.

So, when you exchange order or the two variables you change observed behavior.
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LEARN ABOUT CENTOS

strneqvcmp

strneqvcmp(3)							Programmer's Manual						     strneqvcmp(3)

NAME

       strneqvcmp - compare two strings with an equivalence mapping

SYNOPSIS

       #include <your-opts.h>
       cc [...] -o outfile infile.c -lopts [...]

       int strneqvcmp(char const* str1, char const* str2, int ct);

DESCRIPTION

       Using  a  character  mapping, two strings are compared for "equivalence".  Each input character is mapped to a comparison character and the
       mapped-to characters are compared for the two NUL terminated input strings.  The comparison is limited to ct bytes.  This function name	is
       mapped to option_strneqvcmp so as to not conflict with the POSIX name space.

       str1   first string

       str2   second string

       ct     compare length

RETURN VALUE

       the difference between two differing characters

ERRORS

       none checked.  Caller responsible for seg faults.

SEE ALSO

       The info documentation for the -lopts library.
       ao_string_tokenize(3),  configFileLoad(3), optionFileLoad(3), optionFindNextValue(3), optionFindValue(3), optionFree(3), optionGetValue(3),
       optionLoadLine(3), optionMemberList(3),	optionNextValue(3),  optionOnlyUsage(3),  optionProcess(3),  optionRestore(3),	optionSaveFile(3),
       optionSaveState(3), optionUnloadNested(3), optionVersion(3), strequate(3), streqvcmp(3), streqvmap(3), strtransform(3),

								    2014-06-10							     strneqvcmp(3)
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