c_str() does a SEGSEGV

[shyam]

Hi

I have a program within which i have the following statement.

sprintf(somevar ,"%s/%s.%s",PREFIX.c _str( ),MIDDLE.c_str(
),SUFFIX.c_str( ) );

Here PREFIX, MIDDLE and SUFFIX are all const strings.

This works fine but recently after close to 1000 successful runs my
program dumped with SIGSEGV.

I did a bt on the core file at gdb prompt and found that the problem is
with c_str( )

I am using gcc 3.2.3
libstdc++.so.5

on RH linux AS 3.

Is the spriontf statement correct , or is there any better way.

thanks
Shyam

[Bo Persson]

Thorsten Kiefer wrote:

Hi,
I'm not sure, but I think c_str() allocates new memory which has to
be freed by delete.

If c_str() allocates extra memory, the std::string has to handle the
deallocation itself. User code has to do nothing.
Bo Persson

[Ron Natalie]

shyam wrote:

Ron Natalie wrote:

>shyam wrote:

>>I havent used string or stringstream concatenation.
And i am not using these const strings in any other way.

I feel it is better to concatenate these three strings into one string
object and then so a c_str( ) on that object.

Why? char* is not a #$*&@!@ string. It's a pointer to
a single character. This isn't C.

You are correct but i want the final string in char * form and not C++
string

>string somevar = PREFIX + '/' + MIDDLE + '.' + SUFFIX;

or

ostringstrea m os;
os << PREFIX << "/" << MIDDLE << "." << SUFFIX;
string somevar = os.str();

char* crappy_c_string = new char[somevar.size() + 1];
memcpy(crappy_c _string, somevar.c_str() , somevar.size() + 1];

[Jens Theisen]

"shyam" <sh********@gma il.comwrites:

I have a program within which i have the following statement.

sprintf(somevar ,"%s/%s.%s",PREFIX.c _str( ),MIDDLE.c_str(
),SUFFIX.c_str( ) );

Here PREFIX, MIDDLE and SUFFIX are all const strings.

This works fine but recently after close to 1000 successful runs my
program dumped with SIGSEGV.

snprintf is dangerous and flawed, it should not be used in C code, let
alone C++ code.

For C, use snprintf, for C++, use std::stringstre am and/or
std::string as other have already suggested.

My bet is that your somevar buffer is to small to hold some of your
resulting formatted strings. That's exactly why that function
shouldn't be used.

I did a bt on the core file at gdb prompt and found that the problem is
with c_str( )

That would surprise me. In the above statement, there is nothing wrong
except the potential buffer overflow. What exactly is gdb telling you?

Regards,

Jens