1 files changed, 71 insertions, 4 deletions

diff --git a/Python/pystrtod.c b/Python/pystrtod.c
index 209c9086c8..64d0c52e48 100644
--- a/Python/pystrtod.c
+++ b/Python/pystrtod.c
@@ -370,6 +370,72 @@ PyOS_string_to_double(const char *s,
     return result;
 }
 
+/* Remove underscores that follow the underscore placement rule from
+   the string and then call the `innerfunc` function on the result.
+   It should return a new object or NULL on exception.
+
+   `what` is used for the error message emitted when underscores are detected
+   that don't follow the rule. `arg` is an opaque pointer passed to the inner
+   function.
+
+   This is used to implement underscore-agnostic conversion for floats
+   and complex numbers.
+*/
+PyObject *
+_Py_string_to_number_with_underscores(
+    const char *s, Py_ssize_t orig_len, const char *what, PyObject *obj, void *arg,
+    PyObject *(*innerfunc)(const char *, Py_ssize_t, void *))
+{
+    char prev;
+    const char *p, *last;
+    char *dup, *end;
+    PyObject *result;
+
+    if (strchr(s, '_') == NULL) {
+        return innerfunc(s, orig_len, arg);
+    }
+
+    dup = PyMem_Malloc(orig_len + 1);
+    end = dup;
+    prev = '\0';
+    last = s + orig_len;
+    for (p = s; *p; p++) {
+        if (*p == '_') {
+            /* Underscores are only allowed after digits. */
+            if (!(prev >= '0' && prev <= '9')) {
+                goto error;
+            }
+        }
+        else {
+            *end++ = *p;
+            /* Underscores are only allowed before digits. */
+            if (prev == '_' && !(*p >= '0' && *p <= '9')) {
+                goto error;
+            }
+        }
+        prev = *p;
+    }
+    /* Underscores are not allowed at the end. */
+    if (prev == '_') {
+        goto error;
+    }
+    /* No embedded NULs allowed. */
+    if (p != last) {
+        goto error;
+    }
+    *end = '\0';
+    result = innerfunc(dup, end - dup, arg);
+    PyMem_Free(dup);
+    return result;
+
+  error:
+    PyMem_Free(dup);
+    PyErr_Format(PyExc_ValueError,
+		 "could not convert string to %s: "
+		 "%R", what, obj);
+    return NULL;
+}
+
 #ifdef PY_NO_SHORT_FLOAT_REPR
 
 /* Given a string that may have a decimal point in the current
@@ -881,12 +947,12 @@ PyAPI_FUNC(char *) PyOS_double_to_string(double val,
 #define OFS_E 2
 
 /* The lengths of these are known to the code below, so don't change them */
-static char *lc_float_strings[] = {
+static const char * const lc_float_strings[] = {
     "inf",
     "nan",
     "e",
 };
-static char *uc_float_strings[] = {
+static const char * const uc_float_strings[] = {
     "INF",
     "NAN",
     "E",
@@ -925,7 +991,8 @@ static char *
 format_float_short(double d, char format_code,
                    int mode, int precision,
                    int always_add_sign, int add_dot_0_if_integer,
-                   int use_alt_formatting, char **float_strings, int *type)
+                   int use_alt_formatting, const char * const *float_strings,
+                   int *type)
 {
     char *buf = NULL;
     char *p = NULL;
@@ -1176,7 +1243,7 @@ PyAPI_FUNC(char *) PyOS_double_to_string(double val,
                                          int flags,
                                          int *type)
 {
-    char **float_strings = lc_float_strings;
+    const char * const *float_strings = lc_float_strings;
     int mode;
 
     /* Validate format_code, and map upper and lower case. Compute the