no-reply@allegro.cc (eversojk) — Tue, 18 Feb 2014 17:48:09 +0000

I am currently following a tutorial for Allegro 5 and when trying to use al_draw_text, I get a seg fault. After using gdb, I found that it is looking in my downloads directory for the text addon. Any idea why this would be?

I am on Linux Mint 16, using g++ 4.8.1 and Allegro 5.0.11.

GDB output:

Program received signal SIGSEGV, Segmentation fault.
al_draw_ustr (font=font@entry=0x0, color=..., x=x@entry=50, y=50, flags=flags@entry=0, ustr=0x7fffffffdf80)
    at /home/me/Downloads/allegro/addons/font/text.c:93
93  /home/me/Downloads/allegro/addons/font/text.c: No such file or directory.

GDB backtrace:

#0  al_draw_ustr (font=font@entry=0x0, color=..., x=x@entry=50, y=50, flags=flags@entry=0, ustr=0x7fffffffdf80)
    at /home/me/Downloads/allegro/addons/font/text.c:93
#1  0x00007ffff76f5183 in al_draw_text (font=0x0, color=..., x=50, y=, flags=0, text=)
    at /home/me/Downloads/allegro/addons/font/text.c:106
#2  0x0000000000400c41 in main () at main.cpp:29

My tutorial file:

#SelectExpand
  1#include 
  2#include 
  3#include 
  4#include 
  5
  6int main(void) {
  7    ALLEGRO_DISPLAY *display = NULL;
  8
  9    if (!al_init()) {
 10        al_show_native_message_box(NULL, NULL, NULL,
 11            "failed to initialize allegro!", NULL, ALLEGRO_MESSAGEBOX_ERROR);
 12        return -1;
 13    }
 14
 15    display = al_create_display(640, 480);
 16
 17    if (!display) {
 18        al_show_native_message_box(NULL, NULL, NULL,
 19            "failed to initialize display!", NULL, ALLEGRO_MESSAGEBOX_ERROR);
 20        return -1;
 21    }
 22
 23    al_init_font_addon();
 24    al_init_ttf_addon();
 25
 26    ALLEGRO_FONT *font24 = al_load_font("/usr/share/fonts/truetype/ubuntu-font-family/Ubuntu-Mono-R.ttf", 24, 0);
 27
 28    al_clear_to_color(al_map_rgb(0, 0, 0));
 29    al_draw_text(font24, al_map_rgb(255, 0, 255), 50, 50, 0, "You like my font?");
 30    al_flip_display();
 31    al_rest(3.0);
 32    al_destroy_display(display);
 33
 34    return 0;
 35}

Makefile:

#SelectExpand
  1CXX=g++
  2CFLAGS=
  3LDFLAGS=-L/usr/lib -lallegro -lallegro_dialog -lallegro_font -lallegro_ttf
  4INCLUDE=-I. -I/usr/include/allegro5
  5
  6OBJS=main.cpp
  7OUT=main
  8
  9all: main
 10
 11main: $(OBJS); $(CXX) $(OBJS) -o $(OUT) $(INCLUDE) $(CFLAGS) $(LDFLAGS)
 12
 13debug: $(OBJS); $(CXX) -O0 -g $(OBJS) -o $(OUT) $(INCLUDE) $(CFLAGS) $(LDFLAGS)
 14
 15clean: ; rm -rf *.o main

no-reply@allegro.cc (pkrcel) — Tue, 18 Feb 2014 18:10:56 +0000

Check if the font is actually loaded by verifing the retunr code of al_load_font

From what you posted it seems that GDB is looking for the source file in your downloads directory (which makes sense after all, I guess), but the SegFault seems due to invalid font pointer...which in turn may be caused by a failed load operation.

Someone will point out that you should always check return values...

no-reply@allegro.cc (eversojk) — Tue, 18 Feb 2014 18:23:20 +0000

Thanks! I thought I had checked it but obviously I didn't, works fine now!

no-reply@allegro.cc (Thomas Fjellstrom) — Tue, 18 Feb 2014 18:24:45 +0000

That no such file or directory message is just gdb looking for the source so it can show the source at the line it crashed at. It's not a fatal error or related to the crash at all.

no-reply@allegro.cc (Edgar Reynaldo) — Tue, 18 Feb 2014 23:24:17 +0000

It is looking for the source code in the place it was compiled, which may have been on a different machine.

Looking for addons in wrong directory