More information: I tried to reproduce the error on a different system to which I have access (a Windows box). At precisions 211, 221, 231, 240, 250, and 260 digits, the requested number of digits (or approximately as many, I didn't count) were displayed. At 269, 279, 288, 298, 308, and 317 digits only 19 digits were displayed. I find this both for version [2, 6, 1, 15233, "c50552b"] and version [2, 6, 2, 15328, "1f1731f"], both compiled with (your) 32-bit mingw.