kicad-developers team mailing list archive

[John Beard <john.j.beard@xxxxxxxxx>]

Hi,

Simple patch to fix a use of memset to reset an array of floats and
glm::vec3f's to 0.

This is unsafe, not least as float types have implementation-defined
value representations [1]. Memory-0 = float-0 is true for IEEE-754,
and glm::vec3f happens to not have any book-keeping data that could be
smashed by this (if m_materials contained a std::string or
std::vector, this would be very bad karma), so it does happen to work.

Cheers,

John

[1]: http://www.open-std.org/jtc1/sc22/open/n2356/basic.html#basic.fundamental

From b02038bf470d0c8cb8fd552969f36d51bb8afe6b Mon Sep 17 00:00:00 2001
From: John Beard <john.j.beard@xxxxxxxxx>
Date: Fri, 9 Nov 2018 11:58:38 +0000
Subject: [PATCH] Don't use memset to initialise aggregate of floats.

In C3D_RENDER_OGL_LEGACY::setupMaterial(), the struct
m_materials (which is made up of floats and glm::vec3f's)
is initialised with a memset to 0. This is unsafe, as
floating point value representations in C++ are implementation-
defined (so 0 in memory is not 0-valued for sure).

Use empty-brace aggregate-initialisation, which does the right thing.
---
 .../3d_render_ogl_legacy/c3d_render_ogl_legacy.cpp             | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/3d-viewer/3d_rendering/3d_render_ogl_legacy/c3d_render_ogl_legacy.cpp b/3d-viewer/3d_rendering/3d_render_ogl_legacy/c3d_render_ogl_legacy.cpp
index 6498d0f9b..dc9dd0082 100644
--- a/3d-viewer/3d_rendering/3d_render_ogl_legacy/c3d_render_ogl_legacy.cpp
+++ b/3d-viewer/3d_rendering/3d_render_ogl_legacy/c3d_render_ogl_legacy.cpp
@@ -175,8 +175,7 @@ void C3D_RENDER_OGL_LEGACY::render_3D_arrows()
 
 void C3D_RENDER_OGL_LEGACY::setupMaterials()
 {
-
-    memset( &m_materials, 0, sizeof( m_materials ) );
+    m_materials = {};
 
     if( m_settings.GetFlag( FL_USE_REALISTIC_MODE ) )
     {
-- 
2.19.1