Problem with std::string erase function.

**Chris \( Val \)** · Jul 22 '05, 08:27 PM

Re: Problem with std::string erase function.

"Tero Toivanen" <drei3t@yahoo.c om> wrote in message news:416E29BD.F 838F959@yahoo.c om...
| Dear experts,
|
| I am doing code to Solaris 9 system with C++.
|
| I get every now and then segmentation fault in the following code that
| removes
| heading and trailing white spaces (mLineStr is of type std:string):
|
| ------
|
| 1: void ClassXXX::Funct ionYYY (const std::string & inCmd)
| 2: {
| 3: mLineStr = inCmd;
| 4:
| 5: int tmpSpaceNum = 0;
| 6: int tmpLength = mLineStr.length ();
| 7:
| 8: // remove heading white spaces
| 9: for (int idx1=0; idx1 < tmpLength; idx1++)
| 10: {
| 11: if (isspace( mLineStr [idx1] ))
| 12: {
| 13: tmpSpaceNum++;
| 14: }
| 15: else
| 16: break;
| 17: }
| 18:
| 19: mLineStr.erase (0, tmpSpaceNum);
| 20:
| 21: tmpSpaceNum = 0;
| 22: tmpLength = mLineStr.length ();
| 23:
| 24: // remove trailing whites paces
| 25: for (int idx2=tmpLength-1; idx2 >= 0; idx2--)
| 26: {
| 27: if (isspace( mLineStr [idx2] ))
| 28: {
| 29: tmpSpaceNum++;
| 30: }
| 31: else
| 32: break; // leave the loop
| 33:
| 34: }
| 35:
| 36: mLineStr.erase (tmpLength-tmpSpaceNum, tmpSpaceNum);
|
| -------
|
| Now with mLineStr = "foobar -d jomppe -m4 " there will be segmentation
| fault
| in the last line with a printing to stderr: "Position 20 is greater than
| size 6" . This
| segmentation fault does not come every time, but only every now and
| then. I guess
| the segmentation fault comes because an exception is not catched, but I
| cannot
| understand the reason for the exception!.
|
| Is the memory somehow corrupted or is there some known bugs in erase
| function?
| After all, in line 22 the length of mLineStr still seems to be 21
| characters, but in
| line 36 it is for some reason 6...
|
| Thank you very much in advance,

I wrote myself a little function to do this sort of thing
in the past. Try this:

# include <iostream>
# include <ostream>
# include <string>

inline std::string TrimBS( const std::string& S,
const std::string& Delim = " \a\b\f\t\n\r\v" )
{
const std::string::si ze_type
First( S.find_first_no t_of( Delim ) );

const std::string::si ze_type
Last( S.find_last_not _of( Delim ) );

return ( First == std::string::np os ) ?
std::string( "" ) :
S.substr( First, Last - First + 1 );
}

int main()
{
std::string Buffer( " \t\nExample Test String\n\t\r " );

std::cout << '*' << TrimBS( Buffer ) << '*' << std::endl;

return 0;
}

'TrimBS' returns an copy of the string, so as to preserve
the original, but you can easily change that if you wish.

Good luck.
Chris Val

Problem with std::string erase function.

Problem with std::string erase function.

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