(gdb) bt full
#0  _mesa_error (ctx=0x2872000, error=1282, fmtString=0x7f8c5e29ba6c "glAttachShader") at ../../src/mesa/main/errors.c:984
        do_output = 1 '\001'
        do_log = 1 '\001'
        error_msg_id = 1
        __PRETTY_FUNCTION__ = "_mesa_error"
#1  0x00007f8c5df39775 in attach_shader (ctx=0x2872000, program=16, shader=18) at ../../src/mesa/main/shaderapi.c:242
        shProg = 0x2a9fc90
        sh = 0x2aa2510
        i = 1
        n = 2
        same_type_disallowed = true
#2  0x00007f8c5df3aefb in _mesa_AttachShader (program=16, shader=18) at ../../src/mesa/main/shaderapi.c:1023
        ctx = 0x2872000
#3  0x00007f8c6219f7da in _glamor_create_linear_gradient_program (screen=screen@entry=0x28aa200, stops_count=stops_count@entry=0, dyn_gen=0) at /var/tmp/portage/x11-libs/glamor-9999/work/glamor-9999/src/glamor_gradient.c:615
        glamor_priv = 0x28ad550
        dispatch = 0x28ad550
        index = 0
        gradient_prog = 16
        gradient_fs = 0x2ac5650 " {\n        stop_color_before = stop_color0;\n        stop_color_after = stop_color1;\n        stop_after = stop1;\n        stop_before = stop0;\n    } else if((stop_len < stop2) && (n_stop >= 3)) {\n      "...
        fs_main_prog = 18
        fs_getcolor_prog = 19
        vs_prog = 17
        gradient_vs = 0x7f8c621b3a28 "precision mediump float;\nattribute vec4 v_position;\nattribute vec4 v_texcoord;\nvarying vec2 source_texture;\n\nvoid main()\n{\n    gl_Position = v_position;\n    source_texture = v_texcoord.xy;\n}\n"
#4  0x00007f8c6219fb8d in glamor_init_gradient_shader (screen=screen@entry=0x28aa200) at /var/tmp/portage/x11-libs/glamor-9999/work/glamor-9999/src/glamor_gradient.c:663
        glamor_priv = 0x64616853
        i = <optimized out>
#5  0x00007f8c6218f3c0 in glamor_init (screen=screen@entry=0x28aa200, flags=flags@entry=15) at /var/tmp/portage/x11-libs/glamor-9999/work/glamor-9999/src/glamor.c:429
        glamor_priv = 0x28ad550
        gl_version = <optimized out>
        ps = 0x28ad200
#6  0x00007f8c60b9bbc5 in radeon_glamor_init (screen=screen@entry=0x28aa200) at /var/tmp/portage/x11-drivers/xf86-video-ati-9999/work/xf86-video-ati-9999/src/radeon_glamor.c:253
        scrn = 0x280bf50
#7  0x00007f8c60b52eb1 in RADEONAccelInit (pScreen=pScreen@entry=0x28aa200) at /var/tmp/portage/x11-drivers/xf86-video-ati-9999/work/xf86-video-ati-9999/src/radeon_accel.c:186
        pScrn = <optimized out>
        info = 0x2814bf0
#8  0x00007f8c60b970ce in RADEONScreenInit_KMS (pScreen=0x28aa200, argc=<optimized out>, argv=<optimized out>) at /var/tmp/portage/x11-drivers/xf86-video-ati-9999/work/xf86-video-ati-9999/src/radeon_kms.c:1227
        pScrn = 0x280bf50
        info = 0x2814bf0
        subPixelOrder = <optimized out>
        s = <optimized out>
        front_ptr = 0x0
        ret = <optimized out>
#9  0x0000000000438c70 in AddGPUScreen (pfnInit=0x7f8c60b96c24 <RADEONScreenInit_KMS>, argc=argc@entry=1, argv=argv@entry=0x7fff0cf59158) at /var/tmp/portage/x11-base/xorg-server-1.14.0/work/xorg-server-1.14.0/dix/dispatch.c:3890
        i = 0
        pScreen = 0x28aa200
        ret = 0
#10 0x00000000004794a8 in InitOutput (pScreenInfo=pScreenInfo@entry=0x811d20 <screenInfo>, argc=argc@entry=1, argv=argv@entry=0x7fff0cf59158) at /var/tmp/portage/x11-base/xorg-server-1.14.0/work/xorg-server-1.14.0/hw/xfree86/common/xf86Init.c:857
        pScrn = 0x280bf50
        i = <optimized out>
        j = <optimized out>
        k = <optimized out>
        scr_index = <optimized out>
        modulelist = <optimized out>
        optionlist = 0x27fb840
        screenpix24 = <optimized out>
        pix24 = <optimized out>
        pix24From = <optimized out>
        pix24Fail = 0
        autoconfig = <optimized out>
        sigio_blocked = 0
        want_hw_access = <optimized out>
        configured_device = <optimized out>
#11 0x0000000000428053 in main (argc=1, argv=0x7fff0cf59158, envp=<optimized out>) at /var/tmp/portage/x11-base/xorg-server-1.14.0/work/xorg-server-1.14.0/dix/main.c:204
        i = <optimized out>
        alwaysCheckForInput = {0, 1}