$ pkg-config --modversion x11
1.6.2

Run piglit test glx-tfp on Mesa Software Rasterizer.

$ ./bin/glx-tfp -auto
Segmentation fault (core dumped)

(gdb) bt
#0  _XPutPixel32 (ximage=0x17b0200, x=0, y=<optimized out>, pixel=16711680) at ../../src/ImUtil.c:733
#1  0x00007f6fe63e7cd3 in _XSetImage (srcimg=srcimg@entry=0x17afc50, dstimg=dstimg@entry=0x17b0200, x=0, x@entry=2, y=0, y@entry=24838656) at ../../src/ImUtil.c:949
#2  0x00007f6fe63e3b66 in XGetSubImage (dpy=<optimized out>, d=<optimized out>, x=<optimized out>, y=<optimized out>, width=<optimized out>, height=<optimized out>, 
    plane_mask=plane_mask@entry=18446744073709551615, format=format@entry=2, dest_image=dest_image@entry=0x17b0200, dest_x=dest_x@entry=0, dest_y=dest_y@entry=0)
    at ../../src/GetImage.c:129
#3  0x00007f6fe6739ede in swrastGetImage (read=<optimized out>, x=<optimized out>, y=<optimized out>, w=<optimized out>, h=<optimized out>, data=<optimized out>, 
    loaderPrivate=0x17afe50) at drisw_glx.c:198
#4  0x00007f6fe1ad1fc4 in swrastSetTexBuffer2 (pDRICtx=<optimized out>, target=<optimized out>, texture_format=8409, dPriv=0x17b0290) at swrast.c:103
#5  0x0000000000401b13 in draw_pixmap (pixmap=75497480, x=32, y=32, w=64, h=64) at piglit/tests/glx/glx-tfp.c:143
#6  0x0000000000401cc4 in draw (dpy=0x15a1010) at piglit/tests/glx/glx-tfp.c:175
#7  0x00007f6fe6a1cd11 in piglit_glx_event_loop (dpy=0x15a1010, draw=0x401be2 <draw>) at piglit/tests/util/piglit-glx-util.c:210
#8  0x0000000000402310 in main (argc=2, argv=0x7fff75933008) at piglit/tests/glx/glx-tfp.c:355
(gdb) frame 0
#0  _XPutPixel32 (ximage=0x17b0200, x=0, y=<optimized out>, pixel=16711680) at ../../src/ImUtil.c:733
733	in ../../src/ImUtil.c
(gdb) print addr
$1 = (unsigned char *) 0x0
(gdb) print ximage->data
$2 = 0x0


libX11/src/ImUtil.c
   721  static int _XPutPixel32 (
   722      register XImage *ximage,
   723      int x,
   724      int y,
   725      unsigned long pixel)
   726  {
   727          unsigned char *addr;
   728  
   729          if ((ximage->format == ZPixmap) && (ximage->bits_per_pixel == 32)) {
   730              addr = &((unsigned char *)ximage->data)
   731                          [y * ximage->bytes_per_line + (x << 2)];
   732              if (*((const char *)&byteorderpixel) == ximage->byte_order)
   733                  *((CARD32 *)addr) = pixel;
   734              else if (ximage->byte_order == MSBFirst) {
   735                  addr[0] = pixel >> 24;
   736                  addr[1] = pixel >> 16;
   737                  addr[2] = pixel >> 8;
   738                  addr[3] = pixel;
   739              } else {
   740                  addr[3] = pixel >> 24;
   741                  addr[2] = pixel >> 16;
   742                  addr[1] = pixel >> 8;
   743                  addr[0] = pixel;
   744              }
   745              return 1;
   746          } else {
   747              _XInitImageFuncPtrs(ximage);
   748              return XPutPixel(ximage, x, y, pixel);
   749          }
   750  }