OpenGL 4.5 Buffer Texture : extensions support - opengl

Question

I use OpenGL Version 4.5.0, but somehow I can not make texture_buffer_object extensions work for me ("GL_EXT_texture_buffer_object" or "GL_ARB_texture_buffer_object"). I am quite new with OpenGL, but if I understand right, these extensions are quite old and even already included in the core functionality...
I looked for the extensions with "OpenGL Extensions Viewer 4.1", it says they are supported on my computer, glewGetExtension("GL_EXT_texture_buffer_object") and glewGetExtension("GL_ARB_texture_buffer_object") both also return true.
But the data from the buffer does not appear in the texture sample (in the fragment shader the texture contains only zeros).
So, I thought maybe the extensions are somehow disabled by default, and I included enabling these extensions in my fragment shader:
#version 440 core
#extension GL_ARB_texture_buffer_object : enable
#extension GL_EXT_texture_buffer_object : enable
And now I get such warnings at run-time:
***GLSL Linker Log:
Fragment info
-------------
0(3) : warning C7508: extension ARB_texture_buffer_object not supported
0(4) : warning C7508: extension EXT_texture_buffer_object not supported
Please see the code example below:
//#define GL_TEXTURE_BIND_TARGET GL_TEXTURE2D
#define GL_TEXTURE_BIND_TARGET GL_TEXTURE_BUFFER_EXT
.....
glGenTextures(1, &texObject);
glBindTexture(GL_TEXTURE_BIND_TARGET, texObject);
GLuint bufferObject;
glGenBuffers(1, &bufferObject);
// Make this the current UNPACK buffer (OpenGL is state-based)
glBindBuffer(GL_TEXTURE_BIND_TARGET, bufferObject);
glBufferData(GL_TEXTURE_BIND_TARGET, nWidth*nHeight*4*sizeof(float), NULL, GL_DYNAMIC_DRAW);
float *test = (float *)glMapBuffer(GL_TEXTURE_BIND_TARGET, GL_READ_WRITE);
for(int i=0; i<nWidth*nHeight*4; i++)
test[i] = i/(nWidth*nHeight*4.0);
glUnmapBuffer(GL_TEXTURE_BIND_TARGET);
glTexBufferEXT(GL_TEXTURE_BIND_TARGET, GL_RGBA32F_ARB, bufferObject);
//glTexImage2D(GL_TEXTURE_BIND_TARGET, 0, components, nWidth, nHeight,
// 0, format, GL_UNSIGNED_BYTE, data);
............
So if I use GL_TEXTURE2D target and load some data array directly to the texture, everything works fine. If I use GL_TEXTURE_BUFFER_EXT target and try to load texture from the buffer, then I get an empty texture in the shader.
Note: I have to load texture data from the buffer because in my real project I generate the data on the CUDA side, and the only way (that I know of) to visualize data from CUDA is using such texture buffers.
So, the questions are :
1) why I become no data in the texture, although the OpenGL version is ok, and Extensions Viewer shows the Extensions as supported ?
2) why trying to enable the extensions in the shader fails ?
Edit details : I updated the post, because I found out the reason for "Invalid Enum" error about that I mentioned first, it was caused by glTexParameteri that is not allowed for buffer textures.

Answer 1

I solved this. I was in a hurry and stupidly missed a very important thing on a wiki page:
https://www.opengl.org/wiki/Buffer_Texture
Access in shaders
In GLSL, buffer textures can only be accessed with the texelFetch​ function. This function takes pixel offsets into the texture rather than normalized texture coordinates. The sampler types for buffer textures are samplerBuffer​.
So in GLSL we should use buffer textures like this:
uniform samplerBuffer myTexture;
void main (void)
{
vec4 color = texelFetch(myTexture, [index]);
not like usual textures:
uniform sampler1D myTexture;
void main (void)
{
vec4 color = texture(myTexture, gl_FragCoord.x);
Warnings about not supported extensions : I think I get them because this functionality is included in the core since OpenGL 3.1, so they should not be enabled additionally any more.