Package: libftgl2
Version: 2.1.3~rc5-4+nmu1
Severity: normal
Tags: patch
Dear Maintainer,
using FTTextureFont can lead to a crash with a "Floating Point Exception".
the problem only appears with very large font-sizes.
my system:
integrated intel gfx card (Ivybridge Mobile)
mesa
maximum texture size: 8192
how to reproduce:
- create a FTTextureFont from
/usr/share/fonts/truetype/ttf-dejavu/DejaVuSans.ttf (as found in the
ttf-dejavu-core package)
font=new
FTGLTextureFont("/usr/share/fonts/truetype/ttf-dejavu/DejaVuSans.ttf")
- set the fontsize to something large
font->FaceSize(3033);
- render the font
font->Render("foo");
this will eventually hit the boundaries of the maximum texture size, leading to
a division by zero in src/FTFont/FTTextureFont.cpp:186.
this in turn crashes the host application.
i'm attaching a short demo program (crasher.cpp; based on FTGL's simple.cpp)
that increases the fontsize, until it crashes.
compile with:
$ g++ -o crasher crasher.cpp $(pkg-config --cflags --libs ftgl) -lglut -lGLU
-lGL
i'm also attaching a fix for the problem, that clamps the divisor to be >=1,
thus making a division by zero impossible.
fmgdsar
IOhannes
-- System Information:
Debian Release: jessie/sid
APT prefers unstable
APT policy: (500, 'unstable'), (500, 'testing'), (1, 'experimental')
Architecture: amd64 (x86_64)
Foreign Architectures: i386
Kernel: Linux 3.13-1-amd64 (SMP w/4 CPU cores)
Locale: LANG=en_US.utf8, LC_CTYPE=en_US.utf8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Versions of packages libftgl2 depends on:
ii libc6 2.18-4
ii libfreetype6 2.5.2-1
ii libgcc1 1:4.8.2-19
ii libgl1-mesa-glx [libgl1] 10.1.0-5
ii libglu1-mesa [libglu1] 9.0.0-2
ii libpng12-0 1.2.50-1
ii libstdc++6 4.8.2-19
ii multiarch-support 2.18-4
ii zlib1g 1:1.2.8.dfsg-1
libftgl2 recommends no packages.
libftgl2 suggests no packages.
-- no debconf information
#define FONT_FILE "/usr/share/fonts/truetype/ttf-dejavu/DejaVuSans.ttf"
#include <stdlib.h> // exit()
#include <GL/glut.h>
#include <FTGL/ftgl.h>
static FTFont *font;
static int fontsize=1024;
static void RenderScene(void)
{
char str[10];
GLint w, h;
float scale=72./(float)fontsize;
glGetTexLevelParameteriv(GL_TEXTURE_2D, 0, GL_TEXTURE_WIDTH, &w);
glGetTexLevelParameteriv(GL_TEXTURE_2D, 0, GL_TEXTURE_HEIGHT, &h);
snprintf(str, 9, "%d", fontsize);
str[9]=0;
font->FaceSize(fontsize);
fprintf(stderr, "facesize=%d\ttexture=%dx%d\n", fontsize, w, h);
fontsize+=10;
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glEnable(GL_DEPTH_TEST);
glPushMatrix();
glTranslatef(-260.0, -0.2, 20.0);
glColor3f(1.0, 1.0, 1.0);
glScalef(scale, scale, scale);
font->Render(str);
glPopMatrix();
glutSwapBuffers();
}
//
// Main program entry point: set up GLUT window, load fonts, run GLUT loop.
//
int main(int argc, char **argv)
{
char const *file = NULL;
file = FONT_FILE;
if(argc > 1)
{
file = argv[1];
}
// Initialise GLUT stuff
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_DEPTH | GLUT_DOUBLE | GLUT_RGBA);
glutInitWindowPosition(100, 100);
glutInitWindowSize(640, 480);
glutCreateWindow("simple FTGL C++ demo");
glutDisplayFunc(RenderScene);
glutIdleFunc(RenderScene);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluPerspective(90, 640.0f / 480.0f, 1, 1000);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
gluLookAt(0.0, 0.0, 640.0f / 2.0f, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0);
// Initialise FTGL stuff
font = new FTTextureFont(file);
if(font->Error())
{
fprintf(stderr, "%s: could not load font `%s'\n", argv[0], file);
return EXIT_FAILURE;
}
font->FaceSize(10);
font->Depth(10);
font->Outset(0, 3);
font->CharMap(ft_encoding_unicode);
// Run GLUT loop
glutMainLoop();
return EXIT_SUCCESS;
}
>From eee58e1a78af5439398cc0014809c0e994191d08 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?IOhannes=20m=20zm=C3=B6lnig?=
<zmoel...@umlautq.umlaeute.mur.at>
Date: Mon, 14 Apr 2014 13:41:52 +0200
Subject: [PATCH] fix floating point exception
clamp minimum height of texture to 1, so we don't get a division-by-zero on very large texture sizes
---
src/FTFont/FTTextureFont.cpp | 1 +
1 file changed, 1 insertion(+)
diff --git a/src/FTFont/FTTextureFont.cpp b/src/FTFont/FTTextureFont.cpp
index 4e385ea..4c93598 100644
--- a/src/FTFont/FTTextureFont.cpp
+++ b/src/FTFont/FTTextureFont.cpp
@@ -181,6 +181,7 @@ void FTTextureFontImpl::CalculateTextureSize()
textureWidth = textureWidth > maximumGLTextureSize ? maximumGLTextureSize : textureWidth;
int h = static_cast<int>((textureWidth - (padding * 2)) / glyphWidth + 0.5);
+ if(h<1)h=1;
textureHeight = NextPowerOf2(((numGlyphs / h) + 1) * glyphHeight);
textureHeight = textureHeight > maximumGLTextureSize ? maximumGLTextureSize : textureHeight;
--
1.9.1
