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When running a libchamplain map with GTK and Cogl the call to MapBufferRange actually calls a noop instead.

Attempting to create a point in the libchamplain map will call clutter_actor_constructor() which eventually calls cogl_buffer_map(). I have attached a full backtrace at the end of this issue.

cogl_buffer_map() will try to call mesa's glMapBufferRange in _cogl_buffer_gl_map_range(). The value of ctx->glMapBufferRange in Cogl is set to: (GLvoid *(*)(GLenum, GLintptr, GLsizeiptr, GLbitfield)) 0xfffff5e90828 <shared_dispatch_stub_682>.

With ELF_TLS enabled (the default in mesa) this will branch to the shared_dispatch_stub_682() function which is located at src/mapi/shared-glapi/glapi_mapi_tmp.h:24432 in the build dir.

This then branches to noop_generic() at src/mapi/table.c:61 which is incorrect. Mesa will then return NULL as it was a noop and Cogl will print errors like the one below. This call shouldn't be a noop, but instead should call the corresponding MapBufferRange function.

Cogl-CRITICAL **: 02:29:39.527: _cogl_buffer_gl_map_range: assertion 'data != ((void *)0)' failed
GLib-CRITICAL **: 02:30:24.806: g_error_free: assertion 'error != NULL' filed
Cogl-CRITICAL **: 02:30:24.807: _cogl_buffer_bind_no_create: assertion 'cx->current_buffer[buffer->last_target] != buffer' failed

With ELF_TLS forcefully disabled (a configure patch is required) the problem no longer occurs and the jump happens correctly.

When ELF_TLS is disabled _cogl_buffer_gl_map_range() jumps to mesa's shared_dispatch_stub_682() but in src/mapi/u_current.h:71 instead of the file mentioned above.

This then calls u_current_get_table() in src/mapi/u_current.h and then calls the shared_dispatch_stub_682() function from build/src/mapi/shared-glapi/glapi_mapi_tmp.h:24432. This correctly jumps to _mesa_MapBufferRange() in src/mesa/main/bufferobj.c:3401 and works as expected.

This happens on Debian and OpenEmbedded distros, on both x86_64 and aarch64 systems. This is using glibc as the libc, so is different to #1503 but maybe somewhat related.

Full Backtrace of the mesa call failing:

#0  shared_dispatch_stub_682 (target=35052, offset=0, length=576, access=3)
    at /usr/src/debug/mesa/2_20.0.1-r0/build/src/mapi/shared-glapi/glapi_mapi_tmp.h:24432  #1  0x0000fffff6dbb994 in _cogl_buffer_gl_map_range (buffer=0xffffe000a340, offset=0,          size=576, access=COGL_BUFFER_ACCESS_READ_WRITE, hints=COGL_BUFFER_MAP_HINT_DISCARD,        error=0xffffe7ffdb58) at ../../cogl-1.22.4/cogl/driver/gl/cogl-buffer-gl.c:288
#2  0x0000fffff6dd2584 in cogl_buffer_map_range (buffer=buffer@entry=0xffffe000a340,
    offset=offset@entry=0, size=576, access=access@entry=COGL_BUFFER_ACCESS_READ_WRITE,        hints=hints@entry=COGL_BUFFER_MAP_HINT_DISCARD, error=error@entry=0xffffe7ffdb58)          at ../../cogl-1.22.4/cogl/cogl-buffer.c:263
#3  0x0000fffff6dd26b0 in cogl_buffer_map (buffer=buffer@entry=0xffffe000a340,
    access=access@entry=COGL_BUFFER_ACCESS_READ_WRITE,
    hints=hints@entry=COGL_BUFFER_MAP_HINT_DISCARD)
    at ../../cogl-1.22.4/cogl/cogl-buffer.c:241
#4  0x0000fffff7e619d0 in clutter_canvas_emit_draw (self=0xaaaaab0f33a0)
    at ../../clutter-1.26.2/clutter/clutter-canvas.c:440
#5  clutter_canvas_invalidate (content=0xaaaaab0f33a0)
    at ../../clutter-1.26.2/clutter/clutter-canvas.c:513
#6  0x0000fffff7e69778 in clutter_content_invalidate (
    content=content@entry=0xaaaaab0f33a0)
    at ../../clutter-1.26.2/clutter/clutter-content.c:176
#7  0x0000fffff7e62104 in clutter_canvas_invalidate_internal (height=12,
    width=<optimized out>, canvas=0xaaaaab0f33a0)
    at ../../clutter-1.26.2/clutter/clutter-canvas.c:595
#8  clutter_canvas_set_size (canvas=0xaaaaab0f33a0, width=<optimized out>, height=12)          at ../../clutter-1.26.2/clutter/clutter-canvas.c:637
#9  0x0000fffff7f8910c in champlain_point_init (point=0xffffe0010470)
    at ../git/champlain/champlain-point.c:286
#10 0x0000fffff71ba7d0 in g_type_create_instance (type=<optimized out>)
    at ../glib-2.62.4/gobject/gtype.c:1867
#11 0x0000fffff719cff0 in g_object_constructor (type=<optimized out>,
    n_construct_properties=0, construct_params=0x0)
    at ../glib-2.62.4/gobject/gobject.c:2178
#12 0x0000fffff7e4900c in clutter_actor_constructor (gtype=<optimized out>,
    n_props=<optimized out>, props=<optimized out>)
    at ../../clutter-1.26.2/clutter/clutter-actor.c:6250
#13 0x0000fffff719dae8 in g_object_new_with_custom_constructor (n_params=0, params=0x0,        class=0xffffe000e4e0) at ../glib-2.62.4/gobject/gobject.c:1745
#14 g_object_new_internal (class=class@entry=0xffffe000e4e0, params=params@entry=0x0,          n_params=n_params@entry=0) at ../glib-2.62.4/gobject/gobject.c:1825
#15 0x0000fffff719eb88 in g_object_new_with_properties (object_type=281474439894256,       --Type <RET> for more, q to quit, c to continue without paging--
    n_properties=0, names=names@entry=0x0, values=values@entry=0x0)
    at ../glib-2.62.4/gobject/gobject.c:1995
#16 0x0000fffff719f410 in g_object_new (object_type=<optimized out>,
    first_property_name=first_property_name@entry=0x0)
    at ../glib-2.62.4/gobject/gobject.c:1667
#17 0x0000fffff7f898a8 in champlain_point_new () at ../git/champlain/champlain-point.c:342 #18 0x0000aaaaaaac1d94 in dashsight::track::record::record_page_run ()