c++ - Confused about behaviour of shaders in OpenGL - switching declarations creates errors and crashes -

c++ - Confused about behaviour of shaders in OpenGL - switching declarations creates errors and crashes -

i'm creating functions load shaders, create meshes, , like, started simple programme test functionalities adding, 1 one, , found problem bit:

const char* vertexshader = prm.loadshader ( "simple_vs.glsl" ).c_str (); const char* fragmentshader = prm.loadshader ( "simple_fs.glsl" ).c_str (); gluint vs = glcreateshader ( gl_vertex_shader ); glshadersource ( vs, 1, &vertexshader, null ); glcompileshader ( vs ); gluint fs = glcreateshader ( gl_fragment_shader ); glshadersource ( fs, 1, &fragmentshader, null ); glcompileshader ( fs );

if tried compile it, no errors, there black screen. if removed fragment shader, display triangle, meant to, without colors. if switched 2 declarations, in:

const char* fragmentshader = prm.loadshader ( "simple_fs.glsl" ).c_str (); const char* vertexshader = prm.loadshader ( "simple_vs.glsl" ).c_str ();

i error, , programme crash:

error code #3: shader info shader 1: warning: 0:1: '#version' : version number deprecated in ogl 3.0 forwards compatible context driver error: 0:1: '#extension' : 'gl_arb_separate_shader_objects' not supported

however, if set this:

const char* vertexshader = prm.loadshader ( "simple_vs.glsl" ).c_str (); gluint vs = glcreateshader ( gl_vertex_shader ); glshadersource ( vs, 1, &vertexshader, null ); glcompileshader ( vs ); const char* fragmentshader = prm.loadshader ( "simple_fs.glsl" ).c_str (); gluint fs = glcreateshader ( gl_fragment_shader ); glshadersource ( fs, 1, &fragmentshader, null ); glcompileshader ( fs );

it works fine. clueless why case, ran original code no issues in prior versions of program. checked prm.loadshader function, works fine, , returns expected value. none of changes have made programme deal shaders, confused bizzarely particular behaviour. can more experience explain why happening?

presumably prm.loadshader returns std::string value. calling c_str gives internal character storage of std::string, lives long std::string does. end of each of loadshader lines, std::string returned destroyed because temporary object, , pointers you've stored no longer pointing @ valid character arrays.

you can around storing local re-create of returned strings.

std::string vertexshader = prm.loadshader ( "simple_vs.glsl" ); const char* cvertexshader = vertexshader.c_str(); std::string fragmentshader = prm.loadshader ( "simple_fs.glsl" ); const char* cfragmentshader = vertexshader.c_str(); gluint vs = glcreateshader ( gl_vertex_shader ); glshadersource ( vs, 1, &cvertexshader, null ); glcompileshader ( vs ); gluint fs = glcreateshader ( gl_fragment_shader ); glshadersource ( fs, 1, &cfragmentshader, null ); glcompileshader ( fs );

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