This is a newbie question but I hope I can express my question as clearly as possible.
I'm trying to do pattern matching in C++.
I've downloaded the Win32 version of PCRE from here and I've placed the downloaded pcre3.dll and pcreposix3.dll files into the folder of Dev-CPP's lib folder (I'm using Bloodshed Dev-C++ 4.9.9 IDE).
I've also downloaded a pcrecpp.h header file and have it in the same directory I'm writing the following code (not writing actually. I'm coping example code from a PDF tutorial named PCRE- Perl Compatible Regular Express).
But I can't get it to work. The code is as follows:
#include <iostream>
#include <string>
#include <pcrecpp.h>
using namespace std;
int main()
{
int i;
string s;
pcrecpp::RE re("(\\w+):(\\d+)");
if (re.error().length() > 0) {
cout << "PCRE compilation failed with error: " << re.error() << "\n";
}
if (re.PartialMatch("root:1234", &s, &i))
cout << s << " : " << i << "\n";
}
When I compile the code, Dev-C++ gives me a lot of errors including: "`pcrecpp' has not been declared" and "RE" undeclared.
How should I deal with the downloaded files and fix my problem? Or is there something obvious that I'm missing?
If you specify the file for #include with angle brackets (<>), then the compiler will only look for that header in the locations for external libraries, in so far as the compiler is aware of them.
If you instead use quotation marks (""), then the compiler will also look in the locations for the current project, which typically includes the current directory.
The quick fix for your current problem is to use
#include "pcrecpp.h"
The alternative is to tell the compiler where it can find the headers of the PCRE library.
You will have to tell the compiler where it can find the headers of the PCRE library.
How to do this differs from build system to build system, but if you are using an IDE, then there should be an option somewhere to specify the 'Include directories'. This is where you add the directory of the PCRE headers (with full path).
As a side-note: When the compiler gives you a large number of errors and warnings, always start with fixing the first one. I would guess that in this case it was something like "unable to find header: pcrecpp.h".
It is often the case that, if the compiler tries to continue after encountering a problem, more problems are found that are follow-on problems of the first one. When the first problem is fixed, these also magically disappear.
g++ -lpcrecpp ......
you need to add '-lpcrecpp' to g++ command
cout << “PCRE compilation failed with error: “ << re.error() << “\n”;
I just copied your code and tried to compile it. I got the same error as you reported.
The problem is that string you put to cout is not properly started/ended. You should use real " instead of marks which looks like double quotes (") but it is not. If you fix it, your code should compile w/o any error.
You have included
#include <pcrecpp.h>
1st point to check But is file in the inlcude path of your code. Did you download the installable ? Check where it has been installed on your machine.
2nd point is to check do you have the library paths defined, so that they can be resolved during compiling and linking.
Related
I saw a couple of questions relevant to this topic, but I didn't found the easy and common way to do this.
My question is: How can I have $(projectDir) or another Macro as a string or char* in my C++ code?
Thanks
If your compiler supports raw strings then you can add MYMACRO=R"($(ProjectDir))"; to preprocessor definitions (screenshot from Visual Studio 2013):
Then you can add the following to your code:
#pragma message("MYMACRO == " MYMACRO) // will print project dir during compilation
std::cout << MYMACRO << std::endl; //will print project dir at run time
MYMACRO=R"($(ProjectDir))"; prefectly works for me.
I was in need of this for a long time and this came as a perfect solution.
My test cases took input file path relative to $(ProjectDir) while running the exe tried to locate the input file path relative to the bin folder. As a result, I could have either the VS project happy or the exe, but not both.
This solution worked perfectly to make both of them happy.
Thanks #mvidelgauz for the valuable info.
So finally I’m not able to help myself out by researching anymore. Hopefully you can help me.
I recently decided to learn C++ in the context of my bachelor-thesis: My first aim is to read the pixel-values of a tiff-image with the libtiff-library. Yet, every call of a function of the library seems to break parts of my program.
Here’s the simple “HelloWorld”-Program, it works as it should:
#include "tiffio.h"
#include <iostream>
using namespace std;
int main() {
cout << "Hello" << endl;
// TIFF* tif = TIFFOpen("path to .tif", "r");
return 0;
}
When I uncomment the second line in main(), the code still does compile without errors (except the warning that ‘tif’ isn’t used) and I can start the program as usual. Yet nothing gets printed into the console anymore. Not “Hello” nor any errors.
Any suggestions where the error could be? The code should be alright, I guess I messed something up during the setup of the library or so. Here’s what I did:
I managed to set up eclipse (Mars, 32bit) for C++ and MinGW (32bit) on my 64bit Win7, then downloaded libtiff 4.0.4 and built it following this instruction.
I created a new C++-project with the mentioned code and did the following adjustments in the project-properties:
Project->Properties->C/C++ General->Paths and Symbols->Library
Paths-> Added “D:/… /tiff-4.0.4/libtiff/.libs”
Project->Properties->C/C++ Build->MinGW C++
Linker->Miscellaneous->Set Linkerflags to “-static-libgcc
-static-libstdc++”
Project->Properties->C/C++ Build->MinGW C++ Linker->Libraries-> Set
(-L) to “D:/… /tiff-4.0.4/libtiff/.libs” and (-l) to “libtiff”
I know the .tif is a valid file as I implemented parts of my program in C#, using the LibTiff.NET library by BitMiracle.
Thank you in advance!
Edit 1: The same error occures, even if TIFF* tif = TIFFOpen("path to .tif", "r"); is never called but written down in a dead part of the code. Debugging does not work either, the program seems to be terminated (exit value 0) before a single line is executed, without any error-reports.
I had the same issue and managed to get rid of it.
I set up eclipse (Mars) for C++ and MinGW on my 64bit Win7, then downloaded libtiff 4.0.4 and built it following this instruction.
After the build, I got two directories containing files:
include
tiff.h
tiffconf.h
tiffio.h
tiffio.hxx
tiffvers.h
lib
libtiff.a
libtiff.dll.a
libtiff.la
libtiffxx.a
libtiffxx.dll.a
libtiffxx.la
I also linked all include files and only the libtiff.a to my project and that solved it, ie, the other lines are now executed.
I hope, I helped with this post.
So I bought this book called C++ Programming In Easy Steps by Mike McGrath online.
In the instructions it specifies to create a source file written in C++, the infamous "helo world". So I created my cpp file through sublime text editor and moved it to a file called MyPrograms in my C directory.
The code is as follows:
#include <iostream>
using std::cout;
using std::endl;
int main()
{
cout << "hello world"<< endl ;
return 0 ;
}
I have also tried:
#include
using namespace std;
int main()
{
cout << "hello world"<< endl ;
return 0 ;
}
Ok so I saved this file as hello.cpp in C:\MyPrograms.
Then here is where the error occurs....
I open cmd.
I do "c++"
I receive the message "c++: no input files".Which is what I'm supposed to recieve according to the book.
I proceed to do "cd\myprograms" to enter into the MyPrograms directory.
Once in that directory I do "c++ hello.cpp". According to the book this is supposed to compile my source file and create an executable file next to it. Instead I get a long error message that end in collect 2: 1d returned 1 exit status.
When I visit MyPrograms no executable file has been made next to the original cpp file.
I have also tried to do "c++ hello.cpp -o hello.exe" but it gives me the error again. All of this is done on the command prompt.
Please help :(
It looks to me like MinGW isn't installed properly.
First, it looks like you are trying to use version 4.0.3 but it may be conflicting with a version 3.4.5 that you installed previously (one in c:\mingw and the other in e:\p\giaw\src\pkg).
The latest version of MinGW is 4.7.2.1 which you can install from here: http://www.mingw.org/wiki/InstallationHOWTOforMinGW
But it looks like you're just starting out and it may be better to work with something that's better optimized for Windows (unless you're trying to compile Free Software). You can get a copy of Visual Studio Express for free here:
http://www.visualstudio.com/downloads/download-visual-studio-vs#d-express-windows-desktop
There are older versions available as well if you scroll down (VSE 2010).
main.cpp
#include <iostream>
#include <string>
using namespace std;
void echo(string);
int main()
{
echo("hello");
cout << "Hello world!" << endl;
return 0;
}
print.cpp
#include <iostream>
#include <string>
void echo(string code){
cout << code;
}
After compiling the code in code blocks 12.11, it gives me that error:
undefined reference to `echo(std::string)
I use windows 7 x64.
I have added the directory; Project>build options > search directories and added the current working directory.
All the files are in one console project in code blocks
I believe you should read up a bit more on namespaces usage. You are missing std in print.cpp.
Generally, while starting to learn cpp or getting a grip of the language you should always try writing full names of the classes along with the namespaces. Eventually with practice and some oversights (like now) you will learn why you really need them. In a nutshell namespaces are great:
When you are writing code over multiple files
Compartmentalize your code into separate blocks.
Also, using namespace std; should be used within cpp files mostly (otherwise headers get mangled up.
Anyways, try changing your code to this:
#include <iostream>
#include <string>
void echo(std::string code){
std::cout << code;
}
Then your results will look like this:
> g++ main.cpp print.cpp -o a.out
> ./a.out
helloHello world!
You should get more than that linker error, since you use string without any namespace in your print.cpp file. And if that source file doesn't compile it can't be linked with, and you will get the linker error you have.
Change to e.g.
void echo(std::string code) { ... }
And you do try to link with the object file created from print.cpp ?
I know this is old, but for anyone looking to solve this issue, the following may be a solution for you. If you have g++ follow c++ 11 under project->build options (check your options anyway) then you must check that box for all files you make in the project for the error to be cleared up. I had that annoying undefined reference thing too but now it is gone!
Try "Project/Properties/Build Targets tab". There you should find "Build target files" field. In that filed find "print.cpp" and click the checkbox (now the compiler will build print.cpp).
Some usefull information on Project management in CB
http://www.codeblocks.org/docs/main_codeblocks_en.html
When dealing with strings in C++ its best to sue std::string and your code seems to be wrong with a changes like using std::cout instead of plain cout another thing you need to be careful is linking your files especially files in different directories you need to tell code blocks were to find this print.cpp by going to build option and go for the search tab directory and point to where print.cpp is other wise the other approach is to just build a project which will have the main.cpp and and then add print.cpp class to current project I hope this will be of some help
I downloaded Code::Blocks from here: http://www.codeblocks.org/downloads/26
I'm learning c programming. When I run the following program, I get error:
iostream: No such file or directory
error: syntax error before "namespace"
warning: type defaults to `int' in declaration of `std'
warning: data definition has no type or storage class
In function `main':
error: `cout' undeclared (first use in this function)
error: (Each undeclared identifier is reported only once
error: for each function it appears in.)
error: `cin' undeclared (first use in this function)
I'm running the following program:
#include <iostream>
using namespace std;
int main()
{
int x;
x = 0;
do {
// "Hello, world!" is printed at least one time
// even though the condition is false
cout<<"Hello, world!\n";
} while ( x != 0 );
cin.get();
}
I tried Dev-C++, I get the same error.
How to fix this?
Is this in a file like "program.c" or "program.cpp"? If it's a .c file, then your compiler may be interpreting it as C, and not C++. This could easily cause such an error. It's possible to "force" the compiler to treat either such extension as the other, but by default, .c files are for C, and .cpp files are compiled as C++.
It's either this, or somehow your default "include" directories for the standard library are not set up right, but I don't know how you'd fix that, as that'd be compiler/environment dependent.
I also had that problem when trying to run my first program in Code::Blocks. My file was saved with '.c' extension as 'test.c' and when I saved it as 'test.cpp', it worked fine.
It is also worth mentioning that I had to restart Code::Blocks before new 'test.cpp' file was compiled successfully.
While saving your source code before compiling just save the name with extension ".cpp". You wont get the error..
I got the same problem.
Change #include < iostream.h >
to #incude < iostream >
Consequently, in your program, change every keyword related to iostream, such as cin cout and endl to std::cout, std::cin and std::endl
That'll do the trick
Use <iostream> instead of <iostream.h>
and add std:: before cout, cin etc
Use std::cout << "Welcome";
instead of cout << "Welcome";
Save the file with .cpp extension
you have missing iostream.h file in you mingw directory folder placed inside codeblocks/devc++. what you have to do is just download the file from link given below and replace with your previous mingw folder in codeblocks/devc++.
http://www.4shared.com/rar/owp-D0Km/mingw.html
I found the problem was cause by having a previous version of cgg and cpp in a Perl installation. The Perl structure did not have the correct library files. When I added C:\MinGW\bin and C:\MinGW\MSYS\1.0\bin to the path, I added them at the end so it picked up the Perl install first. I moved the path variable entries to the beginning and reopened my cmd window and it now works because it finds the MinGW version first.
Type path to see your path environment varialble. Mine now looks like:
C:\MinGW>path
PATH=C:\MinGW\bin;C:\MinGW\MSYS\1.0\bin;C:\Perl\site\bin;C:\Perl\bin;C:\WINDOWS\system32;C:\WINDOWS;C:\WINDOWS\System32\Wbem;C:\WINDOWS\System32\WindowsPowerShell\v1.0\;C:\Program Files\WIDCOMM\BluetoothSoftware\;
Apparently you want to create a c++ file. But you allowed your computer to auto provide the file extension C/C++. When it does that it automatically provides a file extension of ".c". Which is not corect. You want ".cpp".
Solution: Rename your file with a ".cpp" extension, or else explicitly state your extension when saving new files by putting ".cpp" (without quotes of course) after your intended file name; i.e. specify your file extension.
I tried in Dev-C++ . Instead of iostream.h use iostream also write the using namespace std;
#include<iostream>
using namespace std;
int main()
{
cout<<"Hello World\n";
return 0;
}
you written your program in C++ code use c code then your program run correctly
in first line use it
#include <Io stream.h>
main ()
{
in ending line use it
system (pause");
You are trying to make a C game right? If you are your code is C++ not C. So if you are trying to make a C game than you should change your code. This might help.
Just put "Using namespace std;" before main() to define the scope of identifiers you are using. This will handle your problem easily.
Try including iostream.h instead of iostream.