Segmentation Fault while std::string assignment

Question

I have a class named Sample which contains a parameter value which is of type std::string. There is a public member function setValue(std::string tempdata) which is used to set the value of this member.

void Sample::setValue( std::string tempdata ) { this->value= tempdata; }

From the application I have to set the value of this parameter. I do something like:

std::string tempvalue = "Hello";
Sample s;
s.setValue( tempvalue );

when I run the application the program crashes and on debugging it through gdb I get:

#0  0x049da761 in __gnu_cxx::__exchange_and_add () from /usr/lib/libstdc++.so.6
#1  0x049c0e6e in std::string::assign () from /usr/lib/libstdc++.so.6
#2  0x049c0ed1 in std::string::operator= () from /usr/lib/libstdc++.so.6
#3  0x08075e9b in Sample::setValue (this=0x83779a8, tempdata=Cannot access memory at address 0xffffffff )

Can anyone please suggest how should I go about debugging this issue?

the code looks ok. Did you modify the header file without recompiling the files which include it ? (e.g. do a make clean and then make if you're working with a Makefile and these targets are defined in it) — Andre Holzner
– Andre Holzner, Commented Sep 17, 2011 at 15:44
This looks like an internal problem of gcc, see stackoverflow.com/questions/7038124/… . — Yaroslav Nikitenko
– Yaroslav Nikitenko, Commented May 13, 2012 at 18:09

Stack Overflow is garbage · Accepted Answer · 2011-09-17 16:43:11Z

2

The code you've shown is correct. So the error is somehere else. It could, for example be stack or heap corruption at some earlier point, which just isn't noticed until these lines of code are executed.

answered Sep 17, 2011 at 16:43

Stack Overflow is garbage

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6 Comments

C. K. Young Over a year ago

Of note is that tempdata is 0xffffffff in the stack trace. That is very...unusual, at least for the code pasted above.

Amit Over a year ago

This code is a part of a bigger application which I am trying to run. It is just that the code crashes at this point when I try to assign a value to class member. I agree this might be a heap or stack corruption but how to look for it in such a large application and does 0xffffffff indicate something significant? - Amit

Stack Overflow is garbage Over a year ago

Well, it indicates that someone wrote the value 0xffffffff to this part of memory at some point. ;) I think @Chris's point is that it's not a commonly-seen value. You more commonly see pointers values that were once valid (pointing to a block of memory that has since been freed), or in debug builds, you might see special values like 0xcdcdcdcd or 0xdeadbeef or other recognizable patterns for uninitialized or freed memory. 0xffffffff is only significant in that it is not the a pointer to either data or code. So someone wrote some non-pointer data over your tempdata pointer.

Stack Overflow is garbage Over a year ago

You could try setting a data breakpoint on the pointer so the debugger will break when the contents of that address are changed.

Amit Over a year ago

I had no idea we could set breakpoints on memory addresses. I will try this out.

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