diff --git a/libc/stdio/stdio.h b/libc/stdio/stdio.h
index dce7bd78..e9598874 100644
--- a/libc/stdio/stdio.h
+++ b/libc/stdio/stdio.h
@@ -2,6 +2,9 @@
 #define COSMOPOLITAN_LIBC_STDIO_STDIO_H_
 #include "libc/fmt/pflink.h"
 #include "libc/runtime/symbolic.h"
+
+#define FILENAME_MAX PATH_MAX
+
 #if !(__ASSEMBLER__ + __LINKER__ + 0)
 COSMOPOLITAN_C_START_
 
diff --git a/third_party/gdtoa/atof.c b/third_party/gdtoa/atof.c
new file mode 100644
index 00000000..1326dfa5
--- /dev/null
+++ b/third_party/gdtoa/atof.c
@@ -0,0 +1,26 @@
+/*-*- 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 2021 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 "third_party/gdtoa/gdtoa.h"
+
+/**
+ * Converts string to double.
+ */
+double atof(const char *s) {
+  return strtod(s, NULL);
+}
diff --git a/third_party/gdtoa/gdtoa.h b/third_party/gdtoa/gdtoa.h
index d5a3f851..4f3f373b 100644
--- a/third_party/gdtoa/gdtoa.h
+++ b/third_party/gdtoa/gdtoa.h
@@ -45,6 +45,7 @@ char *gdtoa(const FPI *fpi, int be, unsigned *bits, int *kindp, int mode,
             int ndigits, int *decpt, char **rve);
 void freedtoa(char *);
 
+double atof(const char *);
 float strtof(const char *, char **);
 double strtod(const char *, char **);
 int strtodg(const char *, char **, const FPI *, int *, unsigned *);