[Mesa-dev] [PATCH 3/4] vbo: replace assert(0) with unreachable()

[Ilia Mirkin]

unreachable is very different from assert(0). Unreachable means "go
into an infinite loop, or other undefined behavior". I haven't checked
the code you're changing, but if it's a complete impossibility for
that case to be hit, then unreachable is fine. Otherwise assert should
be used with a fallback that lets the code limp along instead of
sending the unwitting program into a cpu hang.

On Wed, Jan 17, 2018 at 5:57 PM, Brian Paul <brianp at vmware.com> wrote:
> ---
>  src/mesa/vbo/vbo_context.h    | 8 ++++----
>  src/mesa/vbo/vbo_exec_array.c | 2 +-
>  src/mesa/vbo/vbo_exec_draw.c  | 4 ++--
>  src/mesa/vbo/vbo_save_api.c   | 5 ++---
>  src/mesa/vbo/vbo_save_draw.c  | 2 +-
>  5 files changed, 10 insertions(+), 11 deletions(-)
>
> diff --git a/src/mesa/vbo/vbo_context.h b/src/mesa/vbo/vbo_context.h
> index 04079b7..cd1cbd9 100644
> --- a/src/mesa/vbo/vbo_context.h
> +++ b/src/mesa/vbo/vbo_context.h
> @@ -154,7 +154,7 @@ vbo_draw_method(struct vbo_context *vbo, gl_draw_method method)
>           ctx->Array._DrawArrays = vbo->save.inputs;
>           break;
>        default:
> -         assert(0);
> +         unreachable("Bad VBO drawing method");
>        }
>
>        ctx->NewDriverState |= ctx->DriverFlags.NewArray;
> @@ -178,7 +178,7 @@ vbo_attrtype_to_integer_flag(GLenum format)
>     case GL_UNSIGNED_INT64_ARB:
>        return GL_TRUE;
>     default:
> -      assert(0);
> +      unreachable("Bad vertex attribute type");
>        return GL_FALSE;
>     }
>  }
> @@ -195,7 +195,7 @@ vbo_attrtype_to_double_flag(GLenum format)
>     case GL_DOUBLE:
>        return GL_TRUE;
>     default:
> -      assert(0);
> +      unreachable("Bad vertex attribute type");
>        return GL_FALSE;
>     }
>  }
> @@ -218,7 +218,7 @@ vbo_get_default_vals_as_union(GLenum format)
>     case GL_UNSIGNED_INT:
>        return (fi_type *)default_int;
>     default:
> -      assert(0);
> +      unreachable("Bad vertex format");
>        return NULL;
>     }
>  }
> diff --git a/src/mesa/vbo/vbo_exec_array.c b/src/mesa/vbo/vbo_exec_array.c
> index 024d4d6..16521ff 100644
> --- a/src/mesa/vbo/vbo_exec_array.c
> +++ b/src/mesa/vbo/vbo_exec_array.c
> @@ -150,7 +150,7 @@ check_draw_elements_data(struct gl_context *ctx, GLsizei count,
>           j = ((const GLuint *) elements)[i];
>           break;
>        default:
> -         assert(0);
> +         unreachable("Unexpected index buffer type");
>        }
>
>        /* check element j of each enabled array */
> diff --git a/src/mesa/vbo/vbo_exec_draw.c b/src/mesa/vbo/vbo_exec_draw.c
> index 3aff97e..080d50c 100644
> --- a/src/mesa/vbo/vbo_exec_draw.c
> +++ b/src/mesa/vbo/vbo_exec_draw.c
> @@ -159,7 +159,7 @@ vbo_copy_vertices(struct vbo_exec_context *exec)
>     case PRIM_OUTSIDE_BEGIN_END:
>        return 0;
>     default:
> -      assert(0);
> +      unreachable("Unexpected primitive type");
>        return 0;
>     }
>  }
> @@ -220,7 +220,7 @@ vbo_exec_bind_arrays(struct gl_context *ctx)
>        }
>        break;
>     default:
> -      assert(0);
> +      unreachable("Bad vertex program mode");
>     }
>
>     for (attr = 0; attr < VERT_ATTRIB_MAX ; attr++) {
> diff --git a/src/mesa/vbo/vbo_save_api.c b/src/mesa/vbo/vbo_save_api.c
> index 1c57544..49939ed 100644
> --- a/src/mesa/vbo/vbo_save_api.c
> +++ b/src/mesa/vbo/vbo_save_api.c
> @@ -174,7 +174,7 @@ copy_vertices(struct gl_context *ctx,
>                  sz * sizeof(GLfloat));
>        return i;
>     default:
> -      assert(0);
> +      unreachable("Unexpected primitive type");
>        return 0;
>     }
>  }
> @@ -675,8 +675,7 @@ copy_from_current(struct gl_context *ctx)
>           save->attrptr[i][0] = save->current[i][0];
>           break;
>        case 0:
> -         assert(0);
> -         break;
> +         unreachable("Unexpected vertex attribute size");
>        }
>     }
>  }
> diff --git a/src/mesa/vbo/vbo_save_draw.c b/src/mesa/vbo/vbo_save_draw.c
> index f5c4a90..6bccc85 100644
> --- a/src/mesa/vbo/vbo_save_draw.c
> +++ b/src/mesa/vbo/vbo_save_draw.c
> @@ -194,7 +194,7 @@ bind_vertex_list(struct gl_context *ctx,
>        }
>        break;
>     default:
> -      assert(0);
> +      unreachable("Bad vertex program mode");
>     }
>
>     for (attr = 0; attr < VERT_ATTRIB_MAX; attr++) {
> --
> 2.7.4
>
> _______________________________________________
> mesa-dev mailing list
> mesa-dev at lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/mesa-dev