问题
When I read the instructions I am confused since it says in the instructions to install glew at <VC_ROOT>\include\GL\glew.h and then it says on windows to #include <glew.h> and not #include <GL/glew.h> and I don't know whether this should be before or after #include <GL/glut.h>. I can build the freeglut example so glut appears to be correctly installed and my problem seems to be with building with glew. The complete program that I try to run is
// Two-Dimensional Sierpinski Gasket
// Generated using randomly selected vertices and bisection
#include <windows.h>
#include "Angel.h"
#include <glew.h>
#include <GL/glut.h>
#pragma comment(lib, "glew32.lib")
const int NumPoints = 5000;
//----------------------------------------------------------------------------
void
init( void )
{
vec2 points[NumPoints];
// Specifiy the vertices for a triangle
vec2 vertices[3] = {
vec2( -1.0, -1.0 ), vec2( 0.0, 1.0 ), vec2( 1.0, -1.0 )
};
// Select an arbitrary initial point inside of the triangle
points[0] = vec2( 0.25, 0.50 );
// compute and store N-1 new points
for ( int i = 1; i < NumPoints; ++i ) {
int j = rand() % 3; // pick a vertex at random
// Compute the point halfway between the selected vertex
// and the previous point
points[i] = ( points[i - 1] + vertices[j] ) / 2.0;
}
// Create a vertex array object
GLuint vao;
glGenVertexArrays( 1, &vao );
glBindVertexArray( vao );
// Create and initialize a buffer object
GLuint buffer;
glGenBuffers( 1, &buffer );
glBindBuffer( GL_ARRAY_BUFFER, buffer );
glBufferData( GL_ARRAY_BUFFER, sizeof(points), points, GL_STATIC_DRAW );
// Load shaders and use the resulting shader program
GLuint program = InitShader( "vshader21.glsl", "fshader21.glsl" );
glUseProgram( program );
// Initialize the vertex position attribute from the vertex shader
GLuint loc = glGetAttribLocation( program, "vPosition" );
glEnableVertexAttribArray( loc );
glVertexAttribPointer( loc, 2, GL_FLOAT, GL_FALSE, 0,
BUFFER_OFFSET(0) );
glClearColor( 1.0, 1.0, 1.0, 1.0 ); // white background
}
//----------------------------------------------------------------------------
void
display( void )
{
glClear( GL_COLOR_BUFFER_BIT ); // clear the window
glDrawArrays( GL_POINTS, 0, NumPoints ); // draw the points
glFlush();
}
//----------------------------------------------------------------------------
void
keyboard( unsigned char key, int x, int y )
{
switch ( key ) {
case 033:
exit( EXIT_SUCCESS );
break;
}
}
//----------------------------------------------------------------------------
int
main( int argc, char **argv )
{
glutInit(&argc, argv);
glutInitDisplayMode( GLUT_RGBA );
glutInitWindowSize( 512, 512 );
// If you are using freeglut, the next two lines will check if
// the code is truly 3.2. Otherwise, comment them out
glutInitContextVersion( 3, 1 );
glutInitContextProfile( GLUT_CORE_PROFILE );
glutCreateWindow( "Sierpinski Gasket" );
glewInit();
init();
glutDisplayFunc( display );
glutKeyboardFunc( keyboard );
glutMainLoop();
return 0;
}
The build error I get is when I try to do "build solution" (the two .cpp files can compile if I right-click the file and select compile)
1>------ Build started: Project: 6E test, Configuration: Release Win32 ------
1> InitShader.cpp
1>c:\users\student\downloads\6e_example1_vc10\6e test\code\Angel.h(65): warning C4305: 'initializing' : truncation from 'double' to 'const GLfloat'
1>c:\users\student\downloads\6e_example1_vc10\6e test\code\mat.h(698): warning C4244: '=' : conversion from 'double' to 'GLfloat', possible loss of data
1>c:\users\student\downloads\6e_example1_vc10\6e test\code\mat.h(699): warning C4244: '=' : conversion from 'double' to 'GLfloat', possible loss of data
1>c:\users\student\downloads\6e_example1_vc10\6e test\code\mat.h(700): warning C4244: '=' : conversion from 'double' to 'GLfloat', possible loss of data
1>c:\users\student\downloads\6e_example1_vc10\6e test\code\mat.h(721): warning C4244: '=' : conversion from 'double' to 'GLfloat', possible loss of data
1>c:\users\student\downloads\6e_example1_vc10\6e test\code\mat.h(723): warning C4244: '=' : conversion from 'double' to 'GLfloat', possible loss of data
1>c:\users\student\downloads\6e_example1_vc10\6e test\code\mat.h(726): warning C4244: '=' : conversion from 'double' to 'GLfloat', possible loss of data
1>c:\users\student\downloads\6e_example1_vc10\6e test\code\mat.h(742): warning C4244: '=' : conversion from 'double' to 'GLfloat', possible loss of data
1>..\CODE\InitShader.cpp(16): warning C4996: 'fopen': This function or variable may be unsafe. Consider using fopen_s instead. To disable deprecation, use _CRT_SECURE_NO_WARNINGS. See online help for details.
1> C:\Program Files (x86)\Microsoft Visual Studio 11.0\VC\include\stdio.h(218) : see declaration of 'fopen'
1> example1.cpp
1>c:\users\student\downloads\6e_example1_vc10\6e test\code\Angel.h(65): warning C4305: 'initializing' : truncation from 'double' to 'const GLfloat'
1>c:\users\student\downloads\6e_example1_vc10\6e test\code\mat.h(698): warning C4244: '=' : conversion from 'double' to 'GLfloat', possible loss of data
1>c:\users\student\downloads\6e_example1_vc10\6e test\code\mat.h(699): warning C4244: '=' : conversion from 'double' to 'GLfloat', possible loss of data
1>c:\users\student\downloads\6e_example1_vc10\6e test\code\mat.h(700): warning C4244: '=' : conversion from 'double' to 'GLfloat', possible loss of data
1>c:\users\student\downloads\6e_example1_vc10\6e test\code\mat.h(721): warning C4244: '=' : conversion from 'double' to 'GLfloat', possible loss of data
1>c:\users\student\downloads\6e_example1_vc10\6e test\code\mat.h(723): warning C4244: '=' : conversion from 'double' to 'GLfloat', possible loss of data
1>c:\users\student\downloads\6e_example1_vc10\6e test\code\mat.h(726): warning C4244: '=' : conversion from 'double' to 'GLfloat', possible loss of data
1>c:\users\student\downloads\6e_example1_vc10\6e test\code\mat.h(742): warning C4244: '=' : conversion from 'double' to 'GLfloat', possible loss of data
1>example1.obj : error LNK2001: unresolved external symbol __imp____glewBindBuffer
1>example1.obj : error LNK2001: unresolved external symbol __imp____glewVertexAttribPointer
1>example1.obj : error LNK2001: unresolved external symbol __imp__glewInit@0
1>example1.obj : error LNK2001: unresolved external symbol __imp____glewGenVertexArrays
1>example1.obj : error LNK2001: unresolved external symbol __imp____glewUseProgram
1>example1.obj : error LNK2001: unresolved external symbol __imp____glewBufferData
1>example1.obj : error LNK2001: unresolved external symbol __imp____glewBindVertexArray
1>example1.obj : error LNK2001: unresolved external symbol __imp____glewGetAttribLocation
1>example1.obj : error LNK2001: unresolved external symbol __imp____glewGenBuffers
1>example1.obj : error LNK2001: unresolved external symbol __imp____glewEnableVertexAttribArray
1>InitShader.obj : error LNK2001: unresolved external symbol __imp____glewCreateShader
1>InitShader.obj : error LNK2001: unresolved external symbol __imp____glewGetShaderInfoLog
1>InitShader.obj : error LNK2001: unresolved external symbol __imp____glewLinkProgram
1>InitShader.obj : error LNK2001: unresolved external symbol __imp____glewCompileShader
1>InitShader.obj : error LNK2001: unresolved external symbol __imp____glewShaderSource
1>InitShader.obj : error LNK2001: unresolved external symbol __imp____glewGetProgramiv
1>InitShader.obj : error LNK2001: unresolved external symbol __imp____glewGetShaderiv
1>InitShader.obj : error LNK2001: unresolved external symbol __imp____glewGetProgramInfoLog
1>InitShader.obj : error LNK2001: unresolved external symbol __imp____glewCreateProgram
1>InitShader.obj : error LNK2001: unresolved external symbol __imp____glewAttachShader
1>C:\Users\student\Downloads\6E_example1_VC10\6E test\Release\6E test.exe : fatal error LNK1120: 20 unresolved externals
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========
I have put the glew32.lib in Visual Stuiod's library directory:
I also have glew32.lib in Visual Studio project's linker preferences:
I've also copied glew32.lib to C:\Program Files (x86)\Microsoft SDKs\Windows\v7.0A\Lib but it's not working and generates the build error. What am I doing wrong? It's not working even though I put glew32.lib in C:\Windows\System32 and neither does it work when I put the glew32.lib in the Debug directory. I've even put the download directory as an additional dependency for the VC linker and still it is not working:
The directory where I suppose that glew32.lin should be placed is C:\Program Files (x86)\Microsoft Visual Studio 10.0\VC\lib but placing it there makes no difference. I tried with both Visual Studio 2010 and 2012.
I also notice this discrepancy: Opengl32.lib is not in my VC\lib directory when the manual says that it should be.
The problem seems to be the same as in this question:
Glew problems, unresolved externals
I read on the OpenGL forum that somebody had this problem and it was because they had mixed up the 64 bit version and the 32 bit version and I might too have done that initially but now I checked and it seems to be 32 bit everywhere which makes me woner what the 64 bit version of glew is for if it's only the 32 bit version that we're suppose to use.
回答1:
It is not a problem of #include (header files).
The 'unresolved external symbol' errors are because the linker can't find (resolve) these GLEW methods you call (directly or indirectly).
One usually fixes this by adding something like: -lGLEW or -lglew32
to the linker options, in order to give the linker access to the 'compiled code' of this library.
This can also be done via the pragma command at the beginning of your code, but this trick only works in Visual Studio, and won't work if you try to link your code with gcc for instance.
But in any case, you have to make sure the file in question (here glew32.lib) is found in the library path of the linker.
回答2:
The unresolved external symbol error indicates that the header glew.h is found just fine, but it is unable to find and link the glew32.lib file referenced by your pragma comment. Make sure that glew32.lib is in a path that Visual Studio can reference.
来源：https://stackoverflow.com/questions/16816296/linker-error-with-glew-and-visual-studio-on-windows-7