Make improvements

- Improved async signal safety of read() particularly for longjmp()
- Started adding cancel cleanup handlers for locks / etc on Windows
- Make /dev/tty work better particularly for uses like `foo | less`
- Eagerly read console input into a linked list, so poll can signal
- Fix some libc definitional bugs, which configure scripts detected

libc/mem/putenv.c

@@ -0,0 +1,107 @@
+/*-*- 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                              │
+│                                                                              │
+│ Permission to use, copy, modify, and/or distribute this software for         │
+│ any purpose with or without fee is hereby granted, provided that the         │
+│ above copyright notice and this permission notice appear in all copies.      │
+│                                                                              │
+│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
+│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
+│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
+│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
+│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
+│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
+│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
+│ PERFORMANCE OF THIS SOFTWARE.                                                │
+╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/intrin/getenv.internal.h"
+#include "libc/intrin/leaky.internal.h"
+#include "libc/intrin/strace.internal.h"
+#include "libc/macros.internal.h"
+#include "libc/mem/internal.h"
+#include "libc/mem/mem.h"
+#include "libc/runtime/runtime.h"
+#include "libc/sysv/errfuns.h"
+
+static char **expected;
+static size_t capacity;
+
+static size_t __lenenv(char **env) {
+  char **p = env;
+  while (*p) ++p;
+  return p - env;
+}
+
+static char **__growenv(char **a) {
+  size_t n, c;
+  char **b, **p;
+  if (!a) a = environ;
+  n = a ? __lenenv(a) : 0;
+  c = MAX(8ul, n) << 1;
+  if ((b = malloc(c * sizeof(char *)))) {
+    if (a) {
+      for (p = b; *a;) {
+        *p++ = *a++;
+      }
+    } else {
+      b[0] = 0;
+    }
+    environ = b;
+    expected = b;
+    capacity = c;
+    return b;
+  } else {
+    return 0;
+  }
+}
+
+IGNORE_LEAKS(__growenv)
+
+int __putenv(char *s, bool overwrite) {
+  char **p;
+  struct Env e;
+  if (!(p = environ)) {
+    if (!(p = __growenv(0))) {
+      return -1;
+    }
+  }
+  e = __getenv(p, s);
+  if (e.s && !overwrite) {
+    return 0;
+  }
+  if (e.s) {
+    p[e.i] = s;
+    return 0;
+  }
+  if (p != expected) {
+    capacity = e.i;
+  }
+  if (e.i + 1 >= capacity) {
+    if (!(p = __growenv(p))) {
+      return -1;
+    }
+  }
+  p[e.i + 1] = 0;
+  p[e.i] = s;
+  return 0;
+}
+
+/**
+ * Emplaces environment key=value.
+ *
+ * @param s should be a string that looks like `"name=value"` and it'll
+ *     become part of the environment; changes to its memory will change
+ *     the environment too
+ * @return 0 on success, or non-zero w/ errno on error
+ * @raise ENOMEM if out of memory
+ * @see setenv(), getenv()
+ * @threadunsafe
+ */
+int putenv(char *s) {
+  int rc;
+  rc = __putenv(s, true);
+  STRACE("putenv(%#s) → %d% m", s, rc);
+  return rc;
+}