#34 Empty GLUI_TextBox crashes on window 7

[Anonymous]

I was using glui on Ubuntu without any problems, but when I tried the same code on my Windows 7 it crashed.
I reduced the code to a few lines and I found out that it crashed when I created an empty TextBox.
When I add a text in the TextBox (with set_text) then the program will run, but it will still crash when the text is erased afterwards.

The crash occurs in glutMainLoop and I get a the error "Debug Assertion Failed!".
The file is ...\xstring on line 1575 with the expression "string subscript out of range".

[Nobody/Anonymous]

The issue seems to be that the windows implementation of std::string does slightly different range checking when getting a char at an index. On Linux, if you get the first char of an empty string it will return '\0'. On windows it just screams and dies. Running a release build doesn't crash but it does have a lot of unexpected behavior.

[Nobody/Anonymous]

I too was running into this and have found the specific cause.

In VS2010, the default debug project settings define the preprocessor directive
_ITERATOR_DEBUG_LEVEL=2

This causes code inside xstring to perform range checking on calls to string::operator[], like so:

if _ITERATOR_DEBUG_LEVEL == 2

    if (this->_Mysize <= _Off)

        _DEBUG_ERROR("string subscript out of range");

#elif _ITERATOR_DEBUG_LEVEL == 1
_SCL_SECURE_VALIDATE_RANGE(_Off < this->_Mysize);
#endif / _ITERATOR_DEBUG_LEVEL == 2 /

The variable _Mysize apparently represents string length minus null characters - i.e. the value returned by calling string::length. Therefore the range check fails and
throws an out of range exception.

Solutions:
In debug build configuration, in project properties -> C/C++ -> Preprocessor, add the following directive:

_ITERATOR_DEBUG_LEVEL=0

*note: this is probably not a good idea as the you will lose a number of iterator-related asserts across the entire project, but it is the quick and dirty way to get around the issue.

The other way is to modify a few lines of glui_edittext.cpp to check for an empty string before attempting to access the 0-indexed character object of a string.

For example, following lines starting at line 849 :

for( i=start; i<=end; i++ )
width += char_width( text[i] );

should be modified to something like:

if(!text.empty())
for( i=start; i<=end; i++ )
width += char_width( text[i] );

There are a few more places in the source that should be modified in a similar way. I can post the source with all of my changes if someone wants it.

Hope this helps someone :) Cheers!

[Anonymous]

Would you mind posting your glui fixes nobody :)? What other files need modified? I guess I can just keep updating the code till I find all the situations where the error arises.

[horse-in-bathtub]

I am not a dev of the project, but wouldn't mind to help since I find that some things could be factored back in so I don't revisit them. Apologies for the bad formatting, I have no idea how to do it right. Attached file is nicer.

/***** GLUI_EditText::substring_width() **/

int GLUI_EditText::substring_width( int start, int end )
{
int i, width;

width = 0;

// JOHN: empty text
if (start == end)
return 0;

for( i=start; i<=end; i++ )
width += char_width( text[i] );

return width;
}

/***** GLUI_EditText::update_substring_bounds() **/

int GLUI_EditText::update_substring_bounds( void )
{
int box_width;
int text_len = (int)text.length();
int old_start, old_end;

old_start = substring_start;
old_end = substring_end;

/ Calculate the width of the usable area of the edit box /
box_width = MAX( this->w - this->text_x_offset
- 4 / 2 * the two-line box border /
- 2 * GLUI_EDITTEXT_BOXINNERMARGINX, 0 );

CLAMP( substring_end, 0, MAX(text_len-1,0) );
CLAMP( substring_start, 0, MAX(text_len-1,0) );

// JOHN: avoid checks for empty text
if (text_len == 0) {
return false; / bounds did not change /
}

/****** GLUI_EditText::draw_text() ***/

void GLUI_EditText::draw_text( int x, int y )
{
GLUI_DRAWINGSENTINAL_IDIOM
int text_x, i, sel_lo, sel_hi;

// JOHN: empty text
if (text.size() == 0)
return;

/***** GLUI_EditText::draw_insertion_pt() **/

void GLUI_EditText::draw_insertion_pt( void )
{
int curr_x, i;

if ( NOT can_draw() )
return;

/ Don't draw insertion pt if control is disabled /
if ( NOT enabled )
return;

if ( debug ) dump( stdout, "-> DRAW_INS_PT" );

if ( sel_start != sel_end OR insertion_pt < 0 ) {
return; / Don't draw insertion point if there is a current selection /
}

/ printf( "insertion pt: %d\n", insertion_pt ); /

curr_x = this->x_abs + text_x_offset
+ substring_width( substring_start, substring_end )
+ 2 / The edittext box has a 2-pixel margin /
+ GLUI_EDITTEXT_BOXINNERMARGINX; / plus this many pixels blank space
between the text and the box /

// JOHN: avoid repeat on zero char
if (text.size() > 0)
for( i=substring_end; i>=insertion_pt; i-- ) {
curr_x -= char_width( text[i] );
}

[horse-in-bathtub]

Correction to the above. fixes: 1) Insert position was out of place and 2) no text caused greyed field