Hello,
Hope doing great. I mimic the production code here and would like to know the reason why gcc 8.2 is not throwing any warnings. We provided -Wall and -Wextra. Please let me know the right flag to show the warning during compilation time. Thanks
#include <iostream>
#include <string>
using namespace std;
class Sample {
string name ;
public:
void setData(string value) { name = value; }
string getName() const { return name; } -- Returns a copy of the string
const char* getName1() const { return name.c_str(); } -- Returns a Char* to the actual instance variable
const char * getDestination() { return getName().c_str(); }. – Issue is getName() returns a copy of the actual string which is local to this function. Once the function goes out of scope it return junk values. Why the compiler is not throwing any warnings.
};
int main () {
Sample sample;
sample.setData("ROUTEX_CI");
cout << "String Return Name: " << sample.getName() << "\n";
cout << "Const Char Return Name with Instance Variable: " << sample.getName1() << "\n";
cout << "Const Char Return With Temp Variable Created: " << sample.getDestination() << "\n";
return 0;
}
Different in output between CentOS7/gcc 8.2 compiler and CentOS5/gcc 4.2 compiler for the same code.
CentOS7/gcc 8.2 compiler:
String Return Name: ROUTEX_CI
Const Char Return Name with Instance Variable: ROUTEX_CI
Const Char Return With Temp Variable Created: 7���-
CentOS5/gcc 4.2 compiler:
String Return Name: ROUTEX_CI
Const Char Return Name with Instance Variable: ROUTEX_CI
Const Char Return With Temp Variable Created: ROUTEX_CI
-----Original Message-----
From: Kannuswamy, Nanthakumar
Sent: Wednesday, July 29, 2020 7:38 PM
To: 'Jonathan Wakely' <jwakely.gcc@xxxxxxxxx>
Cc: gcc-help@xxxxxxxxxxx; Ramakrishnan, Murugan <murugan.ramakrishnan@xxxxxxxxxx>
Subject: RE: Need suggestion for using intypes.h features in centos5 gcc 4.1.2 compiler version.
Thanks for your help.
Internal Use Only
-----Original Message-----
From: Jonathan Wakely <jwakely.gcc@xxxxxxxxx>
Sent: Wednesday, July 29, 2020 4:19 PM
To: Kannuswamy, Nanthakumar <nanthakumar.kannuswamy@xxxxxxxxxx>
Cc: gcc-help@xxxxxxxxxxx; Ramakrishnan, Murugan <murugan.ramakrishnan@xxxxxxxxxx>
Subject: Re: Need suggestion for using intypes.h features in centos5 gcc 4.1.2 compiler version.
On Wed, 29 Jul 2020 at 21:56, Kannuswamy, Nanthakumar via Gcc-help <gcc-help@xxxxxxxxxxx> wrote:
>
> Hello All,
>
> We would like to use PRIxxx macros which is defined in <inttypes.h>
> (introduced in C99) in our c++ code base which is running on
> centos5/gcc 4.1.2. When we compiling the following program using gcc
> centos5/4.1.2 its compiled successfully
>
> #include <inttypes.h>
> #include <stdio.h>
>
> Int main() {
> Int val = 10;
> printf("Value is %" PRId32, val);
> return 0;
> }
>
> $> gcc PRImacros.c
> Compiled and run successfully.
>
>
> But at the same time, if we compile above program using centos5/g++
> 4.1.2 comes as part of bundled gcc 4.1.2 package, we got the
> following error
>
> $> g++ PRImacros.cpp
> PRImacros.cpp: In function 'int main()':
> PRImacros.c:8: error: expected `)' before 'PRId32'
>
> Since this PRIxxx is introduced in c99, we tried in the following way
> too, but got the error
>
> $> g++ -std=c99 PRImacros.cpp
> cc1plus: warning: command line option "-std=c99" is valid for C/ObjC
> but not for C++
> PRImacros.c: In function 'int main()':
> PRImacros.c:8: error: expected `)' before 'PRId32'
>
> So our question is, Is it possible to use PRIxxx macros in c++ code running on centos5/g++ 4.1.2? If so, how to use it.
It should work if you use g++ -D__STDC_FORMAT_MACROS
The C99 standard said that the macros should not be defined for C++ unless that macro is defined, and the libc headers on CentOS 5 follow that rule. Later C standards removed that rule, so that the macros should be unconditionally defined for C++ programs.
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