Make more improvements

This change includes many bug fixes, for the NT polyfills, strings,
memory, boot, and math libraries which were discovered by adding more
tools for recreational programming, such as PC emulation. Lemon has also
been vendored because it works so well at parsing languages.

tool/build/lib/demangle.c

@@ -0,0 +1,94 @@
+/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
+│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8                                :vi│
+╞══════════════════════════════════════════════════════════════════════════════╡
+│ Copyright 2020 Justine Alexandra Roberts Tunney                              │
+│                                                                              │
+│ This program is free software; you can redistribute it and/or modify         │
+│ it under the terms of the GNU General Public License as published by         │
+│ the Free Software Foundation; version 2 of the License.                      │
+│                                                                              │
+│ This program is distributed in the hope that it will be useful, but          │
+│ WITHOUT ANY WARRANTY; without even the implied warranty of                   │
+│ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU             │
+│ General Public License for more details.                                     │
+│                                                                              │
+│ You should have received a copy of the GNU General Public License            │
+│ along with this program; if not, write to the Free Software                  │
+│ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA                │
+│ 02110-1301 USA                                                               │
+╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/calls/calls.h"
+#include "libc/calls/hefty/spawn.h"
+#include "libc/macros.h"
+#include "libc/runtime/runtime.h"
+#include "libc/str/str.h"
+#include "tool/build/lib/demangle.h"
+
+struct CxxFilt {
+  int pid;
+  int fds[3];
+} g_cxxfilt;
+
+void CloseCxxFilt(void) {
+  close(g_cxxfilt.fds[0]);
+  close(g_cxxfilt.fds[1]);
+  g_cxxfilt.pid = -1;
+}
+
+void SpawnCxxFilt(void) {
+  int pid;
+  char path[PATH_MAX];
+  if (commandv("c++filt", path)) {
+    g_cxxfilt.fds[0] = -1;
+    g_cxxfilt.fds[1] = -1;
+    g_cxxfilt.fds[2] = 2;
+    if ((pid = spawnve(0, g_cxxfilt.fds, path, (char *const[]){"c++filt", NULL},
+                       environ)) != -1) {
+      atexit(CloseCxxFilt);
+    }
+  } else {
+    pid = -1;
+  }
+  g_cxxfilt.pid = pid;
+}
+
+char *DemangleCxxFilt(char *p, const char *symbol) {
+  int n;
+  char buf[512];
+  bool iscomplicated;
+  if (!g_cxxfilt.pid) SpawnCxxFilt();
+  if (g_cxxfilt.pid == -1) return NULL;
+  if ((n = strlen(symbol)) >= ARRAYLEN(buf)) return NULL;
+  memcpy(buf, symbol, n);
+  buf[n] = '\n';
+  write(g_cxxfilt.fds[0], buf, n + 1);
+  n = read(g_cxxfilt.fds[1], buf, ARRAYLEN(buf));
+  if (n > 1 && buf[n - 1] == '\n') {
+    if (buf[n - 2] == '\r') --n;
+    --n;
+    iscomplicated = memchr(buf, ' ', n) || memchr(buf, '(', n);
+    if (iscomplicated) *p++ = '"';
+    p = mempcpy(p, buf, n);
+    if (iscomplicated) *p++ = '"';
+    *p = '\0';
+    return p;
+  } else {
+    CloseCxxFilt();
+    return NULL;
+  }
+}
+
+/**
+ * Decrypts C++ symbol.
+ *
+ * Decoding these takes roughly the same lines of code as an entire
+ * x86_64 disassembler. That's just for the GNU encoding scheme. So
+ * what we'll do, is just offload this work to the c++filt program.
+ */
+char *Demangle(char *p, const char *symbol) {
+  char *r;
+  if (startswith(symbol, "_Z")) {
+    if ((r = DemangleCxxFilt(p, symbol))) return r;
+  }
+  return stpcpy(p, symbol);
+}