String::assign problems

Code:

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cstr[ getLastCharIndex(cstr) + 1 ] = '\0';
str.assign( cstr );

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Code:

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str.assign( cstr, getLastCharIndex(cstr) + 1 );

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Why does the latter inject garbage into my strings?

The latter assigns one more (uninitialized?, null?) character to the string than cstr has. Null-terminator is not part of std::strings.

Also, how does getLastCharIndex work if the string is not null-terminated?

cstr is not null terminated (the length of the string is stored instead). The latter gets the index i of the last char and tells assign to copy i+1 characters starting from cstr.
I've verified getLastCharIndex returns proper indices. It seems that assign doesn't like non-null-terminated char arrays??

If getLastCharIndex returns the same value as strlen (if the string was null-terminated) are you not assigning one more character than there is in the second version?

In the first version, yes the string obviously has to be null-terminated, because otherwise assign wouldn't know how long it is.

getLastCharIndex returns the index of the last character, which would be equivalent to (strlen - 1) (keep in mind, no null-char here). In the first example, I allocated one extra byte for cstr to be able to assign the '\0'.
Basically, if the string is "bar", then getLastCharIndex returns 2 (the index offset of 'r') and so assigning getLastCharIndex()+1 characters should copy the entire string and nothing more, yet I have no idea where the garbage is coming from?? I can verify the index is correct because the first example writes the null character to the correct address.

Actually I think I just found some larger problems in the ADT surrounding getLastCharIndex that may be causing this. I'll investigate some more. Thanks! and sorry for wasting your time.

Code:

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str.assign( cstr, getLastCharIndex(cstr) + 1 );

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What happens if you remove the +1?