android - Why GLES20.glGetAttribLocation returns different values for different devices? -

i'm trying using opengl2.0 , create multiple cubes in 3d space, android devices.

the code runs in devices, not in others, , don't know why... (all devices have opengl 2.0 supported, , have recent android versions [5.0 or 6.0])

i know problem in -1 return value (see down)

int vertexshader = loadglshader(gles20.gl_vertex_shader, r.raw.vertex); int gridshader = loadglshader(gles20.gl_fragment_shader, r.raw.grid_fragment); int passthroughshader = loadglshader(gles20.gl_fragment_shader, r.raw.fragment_color);       cubeprogram1 = gles20.glcreateprogram();      gles20.glattachshader(cubeprogram1, vertexshader);      gles20.glattachshader(cubeprogram1, passthroughshader);      gles20.gllinkprogram(cubeprogram1);      gles20.gluseprogram(cubeprogram1);      cubepositionparam1 = gles20.glgetattriblocation(cubeprogram1, "a_position");     cubenormalparam1 = gles20.glgetattriblocation(cubeprogram1, "a_normal"); ----> returns -1 value     cubelightposparam1 = gles20.glgetuniformlocation(cubeprogram1, "u_lightpos");     cubemodelparam1 = gles20.glgetuniformlocation(cubeprogram1, "u_model") cubemodelviewparam1 = gles20.glgetuniformlocation(cubeprogram1, "u_mvmatrix");     cubemodelviewprojectionparam1 = gles20.glgetuniformlocation(cubeprogram1, "u_mvp"); 

....

 gles20.glenablevertexattribarray(cubenormalparam1); ---> returns -1 ...  

the cubenormalparam1 = gles20.glgetattriblocation(cubeprogram1, "a_normal"); returns value 2 in devices, , -1 in others. have -1 value, give error , doesn't run...

i'm trying see if vertex_shader have errors can't see problems...

uniform mat4 u_model; uniform mat4 u_mvp; uniform mat4 u_mvmatrix; uniform vec3 u_lightpos;  attribute vec4 a_position; attribute vec4 a_color; attribute vec3 a_normal; attribute vec2 a_texcoordinate;  varying vec4 v_color; varying vec3 v_grid; varying vec2 v_texcoordinate;  void main() {    v_grid = vec3(u_model * a_position);      vec3 modelviewvertex = vec3(u_mvmatrix * a_position);    vec3 modelviewnormal = vec3(u_mvmatrix * vec4(a_normal, 0.0));     float distance = length(u_lightpos - modelviewvertex);    vec3 lightvector = normalize(u_lightpos - modelviewvertex);    float diffuse = max(dot(modelviewnormal, lightvector), 0.5);     diffuse = diffuse * (1.0 / (1.0 + (0.00001 * distance * distance)));    v_color = a_color * diffuse;     v_texcoordinate = a_texcoordinate;     gl_position = u_mvp * a_position; } 

why happen? hardware?

any solution fix this?

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to draw cube i've this:

public void drawcube1() {         cubenumber = 1;          gles20.gluseprogram(cubeprogram1);         gles20.gluniform3fv(cubelightposparam1, 1, lightposineyespace, 0);         // set model in shader, used calculate lighting         gles20.gluniformmatrix4fv(cubemodelparam1, 1, false, modelcube, 0);         // set modelview in shader, used calculate lighting         gles20.gluniformmatrix4fv(cubemodelviewparam1, 1, false, modelview, 0);         // set modelviewprojection matrix in shader.         gles20.gluniformmatrix4fv(cubemodelviewprojectionparam1, 1, false, modelviewprojection1, 0);         // set position of cube         gles20.glvertexattribpointer(                 cubepositionparam1, coords_per_vertex, gles20.gl_float, false, 0, cubevertices);         // set normal positions of cube, again shading         gles20.glvertexattribpointer(cubenormalparam1, 3, gles20.gl_float, false, 0, cubenormals);         // set active texture unit texture unit 0.         gles20.glactivetexture(gles20.gl_texture0);         // bind texture unit.         gles20.glbindtexture(gles20.gl_texture_2d, mtextura1);          islookingatobject_number(cubenumber);          // tell texture uniform sampler use texture in shader binding texture unit 0.         gles20.gluniform1i(mtextureuniform, 0);          gles20.glvertexattribpointer(mtexturecoordinate, 2, gles20.gl_float, false, 0, cubetexture);         gles20.glenablevertexattribarray(mtexturecoordinate);          gles20.glenablevertexattribarray(cubepositionparam1);         gles20.glenablevertexattribarray(cubenormalparam1);          gles20.gldrawarrays(gles20.gl_triangles, 0, 36);         checkglerror("drawing cube");     } 

why gles20.glgetattriblocation returns different values different devices? 

... because different devices have different hardware setting binding tables, , in cases may optimize out redundant computations , repack used attributes save space. exactly why api has function call getting binding locations on device @ runtime; if deterministic constants wouldn't need run-time call @ ...

the fact returns -1 isn't error; showing attribute isn't needed (e.g. defined, can optimized out because doesn't contribute fragment pixel color), shouldn't cause problems.

however mean can't safely assume (e.g.) a_position attribute 0, a_color 1, a_normal 2, etc. if you've hard coded in code it's entirely possible uploading wrong data each attribute. must query binding locations binding numbers use (or use shader-side static binding added in opengl es 3.x).

which actual gl api call setting gl error state?