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From: Simon Wright <simon@pushface.org>
Newsgroups: comp.lang.ada
Subject: Re: OpenGL gl.getstring produces erroneous memory access under
 GLOBE_3D on Mac
Date: Mon, 26 Sep 2016 08:18:43 +0100
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Date: 2016-09-26T08:18:43+01:00
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Roger <rogermc@grapevine.com.au> writes:

> Mac OSX 10.11.6
> XCode 8.0
> GNAT GPL 2016 (20160515-49)
> globe_3d_release_2016-07-05

> However, I have just tried to "Checking for OpenGL functionality" as
> described in Apple's OpenGL Programming Guide for Mac.  However,
> gl.GetString(GL.VENDOR) and other calls to gl.GetString result in:
> raised CONSTRAINT_ERROR : erroneous memory access
>
> even if gl.GetString(GL.VENDOR) is in the only instruction in the
> program.

Same here.

Running under gdb I get

Program received signal SIGSEGV, Segmentation fault.
0x00007fff92286c30 in glGetString ()
   from /System/Library/Frameworks/OpenGL.framework/Versions/A/Libraries/libGL.dylib
(gdb) bt
#0  0x00007fff92286c30 in glGetString ()
   from /System/Library/Frameworks/OpenGL.framework/Versions/A/Libraries/libGL.dylib
#1  0x000000010000602a in gl.getstring (name=vendor)
    at /Users/simon/adapilot/local/sjw/GLOBE_3D/bindings/gl.ads:3780
#2  0x0000000100006b8c in gl.getstring (name=vendor)
    at /Users/simon/adapilot/local/sjw/GLOBE_3D/bindings/gl.adb:66
#3  0x00000001000011d4 in t () at /Users/simon/adapilot/local/sjw/GLOBE_3D/t.adb:4

so I think you've come across a bug in Apple's libGL.