Hi -
I get a seg-fault when I compile and run this simple program.
(seg-fault in first call to strtok). Any clues?
My gcc is "gcc version 4.1.1 20070105 (Red Hat 4.1.1-51)"
#include <string.h>
int main()
{
char *token;
char *line = "LINE TO BE SEPARATED";
char *search = " ";
/* Token will point to "LINE". */
token = strtok(line, search);
/* Token will point to "TO". */
token = strtok(NULL, search);
}
Jan 24 '07
16  2044 
"Rolf Magnus" <ra******@t-online.dewrote in message
news:ep******** *****@news.t-online.com...
Chris Theis wrote:
>Even though strtok is not part of the standard library it's still a valid
function call in C++.
Actually, strtok _is_ part of the standard library.
You're of course right! That was a glitch on my part as I assumed the OP was
referring to what was referred to as the standard template lib.
Cheers
Chris
In article <ej************ *************** *****@4ax.com>,
MrAsm <in*****@invali d.comwrote:
>On Wed, 24 Jan 2007 12:33:52 +0100, "Chris Theis"
<ch*********** **@nospam.cern. chwrote:
>>or a more sophisticated version:
//////////////////////////////////////////////////////////////////////////////
inline std::vector<std ::stringTokeniz eString( const std::string& Text,
const std::string& Delimiters )
Very interesting code.
But may I ask:
1. Why are you defining the function as "inline"?
Is "inline" just for simple stuff like a simple accessor (Get/Set) and
similar...?
I would agree that defining it as inline is at best optional.
>2. Why you are returning the string vector?
Would be better to return the string vector as reference in parameter
list, to avoid copy constructors calls?
This is most likely not the case. You just think it will not be as efficient.
Read about return value optimization (RVO).
e.g.
void TokenizeString(
<<< your params >>>
/* out */ std::vector< std::string & Tokens
);
Peronally, I prefer the other style. It is clearer, easier to write, easier
to read, easier to maintain:
output_t theOutput = theFunct(theInp ut);
or
output_t theOutput(theFu nct(theInput));
vs
output_t theOutput; // Argh an unitialised variable !
theFunct(theInp ut, theOutput);
The first case is kind of natural, easy to read. The compiler probably turns
it into the second case. The second case is second nature to C++ programmers
but not quite as natural to read to others. The last case is by far the worst.
Artificially creating an empty object in an undesirable state, then no way to
immediately know if the following line is a bug:
theFunct(theOut put, theInput);
which will compile if for example this is a string transformation function
that takes a string as input and a string as output.
No, even if RVO didn't exist, 99% of the time I would prefer the first style.
Yan
On Jan 24, 4:24 pm, "Chris Theis" <christian.th.. .@nospam.cern.c h>
wrote:
On Jan 24, 12:38 pm, "Amit Gupta" <emaila...@gmai l.comwrote:
[SNIP]
char *token;
char *line = "LINE TO BE SEPARATED";
char *search = " ";
/* Token will point to "LINE". */
token = strtok(line, search);
/* Token will point to "TO". */
token = strtok(NULL, search);
1. Its not C++, Its C.Please do not top post!
I will really take care to release from bad habit of Top Posting,
the only point i want to make is "think twice when you are using strtok
in code."
I was gone thru very bad debuggin hours (at that time i was knowing
very less about multithreaded code and didn't read/understand man page
of strtok carefully)
>
Even though strtok is not part of the standard library it's still a valid
function call in C++.
2.If you are using C++ then try to find std library function.But which std library function would that be?
3.if you are using C then -- Dont use strtok, or use it with caution
and some Extra Checks for Null and related memory stuff.You're absolutely right on this one, although it does not help the OP a bit
with his problem.
Cheers
Chris
"red floyd" <no*****@here.d udewrote in message
news:FT******** ***********@new ssvr25.news.pro digy.net...
Chris Theis wrote:
You might be tempted for example to attempt to call strtok()
>with string object and thus end up doing somethin like this
strtok( line.c_str(), search);
actually, the above should fail to compile, since strtok() takes a char*
as its first argument, and string::c_str() returns a const char *.
You're absolutely right, but I've (unfortunately) seen compilers silently
getting away with it.
Cheers
Chris
"MrAsm" <in*****@invali d.comwrote in message
news:ej******** *************** *********@4ax.c om...
On Wed, 24 Jan 2007 12:33:52 +0100, "Chris Theis"
<ch************ *@nospam.cern.c hwrote:
>>or a more sophisticated version:
//////////////////////////////////////////////////////////////////////////////
inline std::vector<std ::stringTokeniz eString( const std::string& Text,
const std::string& Delimiters )
Very interesting code.
But may I ask:
1. Why are you defining the function as "inline"?
Is "inline" just for simple stuff like a simple accessor (Get/Set) and
similar...?
Actually the reason was somehow historical 'cause I simply copied and pasted
from my personal toolbox file. However, "inline" is simply a hint for the
compiler and it is actually not bound to follow it. With respect to
optimization the compiler is free to decide whether to inline the code or
not as long as it is guaranteed that the behavior does not change. For
example the rumor that virtual functions are never inlined is still going
around, although this doesn't really hold true as it is up to the compiler
and depends on the context
( http://msdn.microsoft.com/msdnmag/issues/0600/c/).
>
2. Why you are returning the string vector?
Would be better to return the string vector as reference in parameter
list, to avoid copy constructors calls?
Yan already answered this in more detail.
Cheers
Chris
On Jan 24, 3:33 am, "Chris Theis" <christian.th.. .@nospam.cern.c h>
wrote:
"Amit Gupta" <emaila...@gmai l.comwrote in
[...]
}or a more sophisticated version:
//////////////////////////////////////////////////////////////////////////////
inline std::vector<std ::stringTokeniz eString( const std::string& Text,
const std::string& Delimiters )
// Tokenize a passed string with respect to the provided delimiters
//
// e.g.
// string Line = "this_dog_i s mine";
// string Delimiters = " ,:_;#";
// vector<stringWo rdList = TokenizeString( Line, Delimiters );
//////////////////////////////////////////////////////////////////////////////
{
std::vector<std ::stringWordLis t;
std::string::si ze_type Begin, End;
std::string Word;
Begin = Text.find_first _not_of( Delimiters ); // skip blanks or whatever
one finds at the beginning
while( Begin != std::string::np os ) {
End = Text.find_first _of( Delimiters, Begin );
if( End == std::string::np os ) { // we'v reached the end without
finding another delimiter
End = Text.length();
}
Word.assign( Text.begin() + Begin, Text.begin() + End );
WordList.push_b ack( Word );
Begin = Text.find_first _not_of( Delimiters, End);
}
return WordList;
-Thanks
In article <ep**********@c ernne03.cern.ch >, ch************* @nospam.cern.ch says...
[ ... ]
Thus, you might consider doing a simple tokenizer using stringstreams if
applicable:
[ code using stringstream elided ]
or a more sophisticated version:
[ code using find_first_of and find_first_not_ of elided ]
You can combine the two, using stringstreams with delimiters of your
choice. A stream considers something as a delimiter if its associated
locale says that character is whitespace.
One example is at: http://groups.google.com/group/comp....81e95c03be9041
--
Later,
Jerry.
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