I'm using g++ under Fedora to compile an openGL project, which has the line:
textureImage = (GLubyte**)malloc(sizeof(GLubyte*)*RESOURCE_LENGTH);
When compiling, g++ error says:
error: ‘malloc’ was not declared in this scope
Adding #include <cstdlib> doesn't fix the error.
My g++ version is: g++ (GCC) 4.4.5 20101112 (Red Hat 4.4.5-2)
You should use new in C++ code rather than malloc so it becomes new GLubyte*[RESOURCE_LENGTH] instead. When you #include <cstdlib> it will load malloc into namespace std, so refer to std::malloc (or #include <stdlib.h> instead).
You need an additional include. Add <stdlib.h> to your list of includes.
Reproduce this error in g++ on Fedora:
How to reproduce this error as simply as possible:
Put this code in main.c:
#include <stdio.h>
int main(){
int *foo;
foo = (int *) std::malloc(sizeof(int));
*foo = 50;
printf("%d", *foo);
}
Compile it, it returns a compile time error:
el#apollo:~$ g++ -o s main.c
main.c: In function ‘int main()’:
main.c:5:37: error: ‘malloc’ was not declared in this scope
foo = (int *) malloc(sizeof(int));
^
Fix it like this:
#include <stdio.h>
#include <cstdlib>
int main(){
int *foo;
foo = (int *) std::malloc(sizeof(int));
*foo = 50;
printf("%d", *foo);
free(foo);
}
Then it compiles and runs correctly:
el#apollo:~$ g++ -o s main.c
el#apollo:~$ ./s
50
Related
I know there are many similar topics but there are equally many unique mistakes that may lead to this problem (so I think). Therefore I ask, after some research.
My problem is that the compiler, GNU GCC, when compiling one file does not see my namespace declared in another file. The IDE (CodeBlocks) evidently does see it as it auto-completes the name of the namespace. I tried to isolate the problem and came up with this:
File main.cpp:
namespace MyName
{
int MyVar;
}
#include "T1.cpp"
int main()
{
return 0;
}
File T1.cpp:
using namespace MyName;
error: 'MyName' is not a name-space name.
In my project I have a header file, say T1.h, and an implementation file T1.cpp — and MyName isn't accessible in either of them.
Any help or guidance would be appreciated.
What's happening is that CodeBlocks is compiling both main.cpp and T1.cpp. Here is what happens when you try to compile each one:
main.cpp:
$ g++ main.cpp
$
T1.cpp
$ g++ T1.cpp
T1.cpp:1:17: error: ‘MyName’ is not a namespace-name
using namespace MyName;
^
T1.cpp:1:23: error: expected namespace-name before ‘;’ token
using namespace MyName;
^
$
T1.cpp, when compiled on it's own, has no knowledge of MyName. To fix this, don't include .cpp files, and put your declarations in header files.
Edit: From what I gather, this may be a better way to organize your example:
T1.h:
namespace MyName {
extern int MyVar;
}
T1.cpp
#include "T1.h"
int MyName::MyVar = 5;
main.cpp
#include "T1.h"
#include <iostream>
using namespace MyName;
int main()
{
std::cout << MyVar << std::endl;
return 0;
}
Now it will compile correctly:
$ g++ -c T1.cpp -o T1.o
$ g++ -c main.cpp -o main.o
$ g++ T1.o main.o
$ ./a.out
5
I have a basic C++ file like so:
#include <iostream>
using namespace std;
int main() {
float x = rand();
cout << x << endl;
return 0;
}
When I run this through g++ on Ubuntu with g++ test.cpp -o test -std=c++11, I get no errors, and the program runs just fine. But when I run it through g++ on MinGW with the same command, I get the following error:
test.cpp: In function 'int main()':
test.cpp:6:17: error: 'rand' was not declared in this scope
float x = rand();
^
I have GCC version 5.3.0. Attempting to compile with g++ test.cpp -o test.exe -std=gnu++11 or g++ test.cpp -o test.exe -std=c++0x yield the same result.
You must include library for the random function first
i-e
#include < cstdlib >
After that your code will work perfectly
Here is the correct code
#include <iostream>
#include <cstdlib>
using namespace std;
int main() {
float x = rand();
cout << x << endl;
return 0;
}
Some compilers allow you to use random function without including library but standard C++ compilers doesn't allow you.
Hope this will help you
I'm trying compile this code in cmd:
#include <iostream>
#include <string>
using namespace std;
int main(){
int n = 24;
string s = to_string(n);
cout<<s;
}
I found in another qestions, that I should use this command:
g++ -std=c++11 main.cpp
but I get error:
main.cpp: In function 'int main()':
main.cpp:7:24: error: 'to_string' was not declared in this scope
string s = to_string(n);
^
I have latest g++ compiler for Windows v. 5.3.0. I used this installer for MinGW.
I tried solve in to_string is not a member of std, says g++, but this patch doesn't work.
How can I compile this code in command line in Windows?
Below is a simple test.c code using curl:
#include <stdio.h>
#include <curl/curl.h>
int main(){
return 0;
}
To compile this code I use:
gcc test1.c -lcurl -o test1
For test1.c above compilation is correct. Now I would like to write some code using C++ libs (curlpp) and after that compile it.
#include <iostream>
#include <curlpp/cURLpp.hpp>
#include <curlpp/Easy.hpp>
#include <curlpp/Options.hpp>
int main(){
return 0;
}
To compile this code I tried:
g++ test2.cpp -lcurl -o test2
But I get this error:
fatal error: curlpp/cURLpp.hpp no such file or directory
compilation terminated.
This formula is not correct. The question is how to compile second code - test2.cpp?
You most likely forgot to install libcurlpp-dev.
You can find out where the required header files are located by running:
$ dpkg -S cURLpp.hpp
libcurlpp-dev:amd64: /usr/include/curlpp/cURLpp.hpp
My program which JIT compiles a LLVM IR module and calls a function foo defined therein fails at runtime if foo uses an externally-defined function:
LLVM ERROR: Program used external function 'glutInit' which could not be resolved!
My program:
// foo1.cpp
#include <GL/glut.h>
extern "C" void foo()
{
glutInit(0,0);
}
// foo2.cpp
#include <iostream>
#include <fstream>
#include <string>
#include <llvm/Support/raw_ostream.h>
#include <llvm/LLVMContext.h>
#include <llvm/Support/TargetSelect.h>
#include <llvm/Support/IRReader.h>
#include <llvm/ExecutionEngine/ExecutionEngine.h>
#include <llvm/Support/MemoryBuffer.h>
#include <llvm/ExecutionEngine/JIT.h>
#include <llvm/ExecutionEngine/RuntimeDyld.h>
int main(int argc, char **argv)
{
using namespace llvm;
InitializeNativeTarget();
LLVMContext context;
SMDiagnostic error;
std::ifstream ir_file("foo1.s");
std::string ir((std::istreambuf_iterator<char>(ir_file)),
(std::istreambuf_iterator<char>()));
Module *m = ParseIR(MemoryBuffer::getMemBuffer(StringRef(ir)), error, context);
if(!m)
{
error.print(argv[0], errs());
}
ExecutionEngine *ee = ExecutionEngine::create(m);
Function *func = ee->FindFunctionNamed("foo");
if(func == 0)
{
std::cerr << "Couldn't find Function foo" << std::endl;
std::exit(-1);
}
typedef void (*fcn_ptr)();
fcn_ptr foo = reinterpret_cast<fcn_ptr>(ee->getPointerToFunction(func));
foo();
delete ee;
return 0;
}
Here's how I build my program:
$ clang -S -emit-llvm foo1.cpp
$ g++ -rdynamic foo2.cpp `llvm-config --cxxflags` `llvm-config --libs` `llvm-config --ldflags` -lglut
The output:
$ ./a.out
LLVM ERROR: Program used external function 'glutInit' which could not be resolved!
It fails with a similar error any time I try to use an externally-defined function which is not in the C++ standard library (e.g., printf, malloc, & free are no problem). What am I doing wrong?
Make sure that glutInit was linked into a.out. If your host code (the thing executing the JIT) didn't call it, it could have been nixed by the linker. If that's the case, you have to add a dummy reference to it or use linker scripts / flags.
Adding the command line option -Wl,-no-as-needed immediately before -lglut will prevent the linker from dropping the glut library, which it otherwise thinks is not needed:
$ g++ -rdynamic foo2.cpp `llvm-config --cxxflags` `llvm-config --libs` `llvm-config --ldflags` -Wl,-no-as-needed -lglut