Strange behaviour using in/out block data with OpenGL/GLSL - opengl

Question

I have implemented normal mapping shader in my OpenGL/GLSL application. To compute the bump and shadow factor in the fragment shader I need to send from the vertex shader some data like the light direction in tangent space and the vertex position in light space for each light of my scene. So to do job I need the declare 2 output variables like below (vertex shader):
#define MAX_LIGHT_COUNT 5
[...]
out vec4 ShadowCoords[MAX_LIGHT_COUNT]; //Vertex position in light space
out vec3 lightDir_TS[MAX_LIGHT_COUNT]; //light direction in tangent space
uniform int LightCount;
[...]
for (int idx = 0; idx < LightCount; idx++)
{
[...]
lightDir_TS[idx] = TBN * lightDir_CS;
ShadowCoords[idx] = ShadowInfos[idx].ShadowMatrix * VertexPosition;
[...]
}
And in the fragment shader I recover these variables thanks to the followings input declarations:
in vec3 lightDir_TS[MAX_LIGHT_COUNT];
in vec4 ShadowCoords[MAX_LIGHT_COUNT];
The rest of the code is not important to explain my problem.
So now here's the result in image:
As you can see until here all is ok!
But now, for a sake of simplicity I want to use a single output declaration rather than 2! So the logical choice is to use an input/output data block like below:
#define MAX_LIGHT_COUNT 5
[...]
out LightData_VS
{
vec3 lightDir_TS;
vec4 ShadowCoords;
} LightData_OUT[MAX_LIGHT_COUNT];
uniform int LightCount;
[...]
for (int idx = 0; idx < LightCount; idx++)
{
[...]
LightData_OUT[idx].lightDir_TS = TBN * lightDir_CS;
LightData_OUT[idx].ShadowCoords = ShadowInfos[idx].ShadowMatrix * VertexPosition;
[...]
}
And in the fragment shader the input data block:
in LightData_VS
{
vec3 lightDir_TS;
vec4 ShadowCoords;
} LightData_IN[MAX_LIGHT_COUNT];
But this time when I execute my program I have the following display:
As you can see the specular light is not the same than in the first case above!
However I noticed if I replace the line:
for (int idx = 0; idx < LightCount; idx++) //Use 'LightCount' uniform variable
by the following one:
for (int idx = 0; idx < 1; idx++) //'1' value hard coded
or
int count = 1;
for (int idx = 0; idx < count; idx++)
the shading result is correct!
The problem seems to come from the fact I use uniform variable in the 'for' condition. However this works when I used seperates output variables like in the first case!
I checked: the uniform variable 'LightCount' is correct and equal to '1'; (I tried unsigned int data type without success and it's the same thing using a 'while' loop)
How can you explain a such result?
I use:
OpenGL: 4.4.0 NVIDIA driver 344.75
GLSL: 4.40 NVIDIA via Cg compiler
I already used input/output data block without problem but it was not arrays but just simple blocks like below:
[in/out] VertexData_VS
{
vec3 viewDir_TS;
vec4 Position_CS;
vec3 Normal_CS;
vec2 TexCoords;
} VertexData_[IN/OUT];
Do you think it's not possible to use input/output data blocks as arrays in a loop using a uniform variable in the for conditions ?
UPDATE
I tried using 2 vec4 (for a sake of data alignment like for uniform block (for this case data need to be aligned on a vec4)) into the data structure like below:
[in/out] LightData_VS
{
vec4 lightDir_TS; //vec4((TBN * lightDir_CS), 0.0f);
vec4 ShadowCoords;
} LightData_[IN/OUT][MAX_LIGHT_COUNT];
without success...
UPDATE 2
Here's the code concerning shader compilation log:
core::FileSystem file(filename);
std::ifstream ifs(file.GetFullName());
if (ifs)
{
GLint compilationError = 0;
std::string fileContent, line;
char const *sourceCode;
while (std::getline(ifs, line, '\n'))
fileContent.append(line + '\n');
sourceCode = fileContent.c_str();
ifs.close();
this->m_Handle = glCreateShader(this->m_Type);
glShaderSource(this->m_Handle, 1, &sourceCode, 0);
glCompileShader(this->m_Handle);
glGetShaderiv(this->m_Handle, GL_COMPILE_STATUS, &compilationError);
if (compilationError != GL_TRUE)
{
GLint errorSize = 0;
glGetShaderiv(this->m_Handle, GL_INFO_LOG_LENGTH, &errorSize);
char *errorStr = new char[errorSize + 1];
glGetShaderInfoLog(this->m_Handle, errorSize, &errorSize, errorStr);
errorStr[errorSize] = '\0';
std::cout << errorStr << std::endl;
delete[] errorStr;
glDeleteShader(this->m_Handle);
}
}
And the code concerning the program log:
GLint errorLink = 0;
glGetProgramiv(this->m_Handle, GL_LINK_STATUS, &errorLink);
if (errorLink != GL_TRUE)
{
GLint sizeError = 0;
glGetProgramiv(this->m_Handle, GL_INFO_LOG_LENGTH, &sizeError);
char *error = new char[sizeError + 1];
glGetShaderInfoLog(this->m_Handle, sizeError, &sizeError, error);
error[sizeError] = '\0';
std::cerr << error << std::endl;
glDeleteProgram(this->m_Handle);
delete[] error;
}
Unfortunatly, I don't have any error log!