Login or Register to Ask a Question and Join Our Community

Sponsored Content
Full Discussion: conversion to 'char' from 'int' warning
Top Forums Programming conversion to 'char' from 'int' warning Post 302478326 by achenle on Tuesday 7th of December 2010 04:24:43 PM
Old 12-07-2010
The declaration for tolower() is:

Code:
int tolower( int );

The function takes an int argument, and returns an int result. Since the cast from char to int is probably from 8 to 16 bits, no data is lost. But on the cast back to char from the int return, the change from 16 to 8 bits means data could be lost.

Of course, changing the contents of the string object passed to ToLower() isn't going to change the contents of the string in the calling code. Since the object is passed by value, the object that the ToLower() method operates on is a copy of the object in the calling code. For example, this code

Code:
#include <ctype.h>
#include <string>
#include <iostream>

using namespace std;

void toLowerVal( string str )
{
    for ( int ii = 0; ii < str.length(); ii++ )
    {
        str[ ii ] = ( char ) ::tolower( str[ ii ] );
    }
}

void toLowerRef( string &str )
{
    for ( int ii = 0; ii < str.length(); ii++ )
    {
        str[ ii ] = ( char ) ::tolower( str[ ii ] );
    }
}

int main( int argc, char **argv )
{
    for ( int ii = 1; ii < argc; ii++ )
    {
        string s1 = argv[ ii ];
        cout << s1 << endl;
        toLowerVal( s1 );
        cout << s1 << endl;
        toLowerRef( s1 );
        cout << s1 << endl;
    }

    return( 0 );
}

produces this output:

Code:
bash-3.2$ ./str ASDf as1FFFF
ASDf
ASDf
asdf
as1FFFF
as1FFFF
as1ffff

Note that calls to toLowerVal() do not change the data contained in the calling code.
 

10 More Discussions You Might Find Interesting

1. Programming

char to int64 conversion

Hi, I'm converting a C program that I made using the Visual Studio. I now use GCC (over Linux) and can't find some equivalences. I changed my __int64 definitions to unsigned long long, but can't find an equivalent to the microsoft i64toa() function, which let you convert a char* to a 64 bit... (1 Reply)
Discussion started by: Raspoutine
1 Replies

2. UNIX for Dummies Questions & Answers

int open(const char *pathname, int flags, mode_t mode) doubt...

hello everybody! I want to create a file with permissions for read, write, and execute to everybody using C, so I write this code: #include <stdio.h> #include <sys/types.h> #include <sys/stat.h> #include <fcntl.h> int main(){ int fileDescriptor; fileDescriptor =... (2 Replies)
Discussion started by: csnmgeek
2 Replies

3. UNIX for Dummies Questions & Answers

ANSI C, char to hex conversion

Hi, I have a char buf,ch; and the buf is filled with the result from MySQL server which I get like this numbytes = recv(sock, buf, 1024, 0));I have the followingcode to display the results printf("received %ld bytes:\n",numbytes); for(c=0;c<numbytes;c++){ ch = (char)buf; ... (2 Replies)
Discussion started by: alikims
2 Replies

4. Programming

Handle int listen(int sockfd, int backlog) in TCP

Hi, from the manual listen(2): listen for connections on socket - Linux man page It has a parameter called backlog and it limits the maximum length of queue of pending list. If I set backlog to 128, is it means no more than 128 packets can be handled by server? If I have three... (3 Replies)
Discussion started by: sehang
3 Replies

5. Programming

error: invalid conversion from ‘const char*’ to ‘char*’

Compiling xpp (The X Printing Panel) on SL6 (RHEL6 essentially): xpp.cxx: In constructor ‘printFiles::printFiles(int, char**, int&)’: xpp.cxx:200: error: invalid conversion from ‘const char*’ to ‘char*’ The same error with all c++ constructors - gcc 4.4.4. If anyone can throw any light on... (8 Replies)
Discussion started by: GSO
8 Replies

6. Programming

Help with understanding ( int, char, long, short, signed, unsigned etc.... )

My question is simple: When should I use a long, int, char, unsigned/signed variables?? When I declare a variable "unsigned;" what did I do it??? Why would I delcare an integer "long" or "short" ( unsigned or signed)?? Any examples of when things like "unsigned", "long", "short" etc...... (6 Replies)
Discussion started by: cpp_beginner
6 Replies

7. Programming

Small query regarding function "char * strerror(int errnum)"

As this function returns the address of the string corressponding to the errno value provided to it. Can someone please let me know where, in the memory, it could be (on freeBSD). The MAN page tells under the BUG section that "For unknown error numbers, the strerror() function will return its... (5 Replies)
Discussion started by: Praveen_218
5 Replies

8. Programming

Double to const char conversion

Dear all, I am using C and ROOT for programming. And I need to incorporate following in my code. char *fps=NULL; int dec=0,sign=0; float mean = h1->GetMean(1); //0.001298 fps= fcvt(mean,6 , &dec, &sign); I need to provide this mean as const char to some other function to get... (8 Replies)
Discussion started by: emily
8 Replies

9. Programming

Invalid conversion from char* to char

Pointers are seeming to get the best of me and I get that error in my program. Here is the code #include <stdio.h> #include <stdlib.h> #include <string.h> #define REPORTHEADING1 " Employee Pay Hours Gross Tax Net\n" #define REPORTHEADING2 " Name ... (1 Reply)
Discussion started by: Plum
1 Replies

10. Programming

Bool vs char * conversion

I have a problem at make step to install a downloaded package consisted of different programs. In file included from kcdbext.cc:16:0: kcdbext.h: In member function �char* kyotocabinet::IndexDB::get(const char*, size_t, size_t*)’: kcdbext.h:1281:14: error: cannot convert �bool’ to... (3 Replies)
Discussion started by: yifangt
3 Replies

LEARN ABOUT MOJAVE

curs_instr

curs_instr(3X)															    curs_instr(3X)

NAME

       instr, innstr, winstr, winnstr, mvinstr, mvinnstr, mvwinstr, mvwinnstr - get a string of characters from a curses window

SYNOPSIS

       #include <curses.h>

       int instr(char *str);
       int innstr(char *str, int n);
       int winstr(WINDOW *win, char *str);
       int winnstr(WINDOW *win, char *str, int n);
       int mvinstr(int y, int x, char *str);
       int mvinnstr(int y, int x, char *str, int n);
       int mvwinstr(WINDOW *win, int y, int x, char *str);
       int mvwinnstr(WINDOW *win, int y, int x, char *str, int n);

DESCRIPTION

       These routines return a string of characters in str, extracted starting at the current cursor position in the named window.  Attributes are
       stripped from the characters.  The four functions with n as the last argument return a leading substring at most n characters long  (exclu-
       sive of the trailing NUL).

RETURN VALUE

       All of the functions return ERR upon failure, or the number of characters actually read into the string.

       X/Open  defines	no  error  conditions.	 In  this  implementation, if the window parameter is null or the str parameter is null, a zero is
       returned.

NOTES

       Note that all routines except winnstr may be macros.

PORTABILITY

       SVr4 does not document whether a length limit includes or excludes the trailing NUL.

       The ncurses library extends the XSI description by allowing a negative value for n.  In this case, the functions return the  string  ending
       at the right margin.

SEE ALSO

       curses(3X).

																    curs_instr(3X)
All times are GMT -4. The time now is 11:14 PM.
Unix & Linux Forums Content Copyright 1993-2022. All Rights Reserved.
Privacy Policy