removed some gcc warnings

openglcanvas.cpp

@@ -136,7 +136,10 @@ void OpenGLCanvas::initializeGL(){
     glHint(GL_PERSPECTIVE_CORRECTION_HINT,GL_NICEST);
 
     char *input_image=(char*)malloc(512*sizeof(char*));
-    GET_WORKDIR(input_image,512);
+    if(!GET_WORKDIR(input_image,512)){
+        fprintf(stderr,"too long pathname\n");
+        exit(-1);
+    };
     strcat(input_image,"/\0");
     strcat(input_image,INPUT_IMAGE_FILE);
 #ifdef __APPLE__
@@ -497,13 +500,19 @@ void OpenGLCanvas::setShaders() {
     GLuint f = glCreateShader(GL_FRAGMENT_SHADER);
 
     char *vs_file=(char*)malloc(512*sizeof(char*));
-    GET_WORKDIR(vs_file,512);
+    if(!GET_WORKDIR(vs_file,512)){
+        fprintf(stderr,"too long pathname\n");
+        exit(-1);
+    };
     strcat(vs_file,"/\0");
     strcat(vs_file,VERT_SHADER_FILE);
     fprintf(stderr,"vs_file=%s\n",vs_file);
 
     char *fs_file=(char*)malloc(512*sizeof(char*));
-    GET_WORKDIR(fs_file,512);
+    if(!GET_WORKDIR(fs_file,512)){
+        fprintf(stderr,"too long pathname\n");
+        exit(-1);
+    };
     strcat(fs_file,"/\0");
     strcat(fs_file,FRAG_SHADER_FILE);
     fprintf(stderr,"fs_file=%s\n",fs_file);
@@ -558,7 +567,7 @@ void OpenGLCanvas::paintGL(){
 
     // defining transformation parameters (that will be passed to the vertex shader)
     float extent = calculate_extent(fov_rads);
-    float vis_mode;
+    float vis_mode=.0;
     if (visualization=="Perspective") vis_mode=1.0;
     else if (visualization=="3D Sphere") vis_mode=2.0;
     else if (visualization=="Equi-Rectangular") vis_mode=3.0;