py/parsenum: Fix parsing LLONG_MIN in longlong configuration.

Re-organize `mp_parse_num_integer()` (for longlong) slightly so that the
most negative 64-bit integer can be parsed.

Fixes issue #17932.

Signed-off-by: Jeff Epler <jepler@gmail.com>

py/objint.c

@@ -247,7 +247,7 @@ char *mp_obj_int_formatted(char **buf, size_t *buf_size, size_t *fmt_size, mp_co
 
     char sign = '\0';
     if (num < 0) {
-        num = -num;
+        num = -(fmt_uint_t)num;
         sign = '-';
     }
 

py/parsenum.c

@@ -64,7 +64,7 @@ typedef mp_int_t parsed_int_t;
 typedef unsigned long long parsed_int_t;
 
 #define PARSED_INT_MUL_OVERFLOW mp_mul_ull_overflow
-#define PARSED_INT_FITS(I) ((I) <= (unsigned long long)LLONG_MAX)
+#define PARSED_INT_FITS(I) ((I) <= (unsigned long long)LLONG_MAX + 1)
 #endif
 
 mp_obj_t mp_parse_num_integer(const char *restrict str_, size_t len, int base, mp_lexer_t *lex) {
@@ -135,8 +135,11 @@ mp_obj_t mp_parse_num_integer(const char *restrict str_, size_t len, int base, m
 have_ret_val:
     #else
     // The PARSED_INT_FITS check above ensures parsed_val won't overflow signed long long
-    long long signed_val = parsed_val;
-    if (neg) {
+    long long signed_val = -parsed_val;
+    if (!neg) {
+        if (signed_val == LLONG_MIN) {
+            goto overflow;
+        }
         signed_val = -signed_val;
     }
     ret_val = mp_obj_new_int_from_ll(signed_val); // Could be large or small int

tests/basics/int_64_basics.py

@@ -151,3 +151,11 @@ try:
     print((1 << 48) << -6)
 except ValueError as e:
     print(e)
+
+# Test that the most extreme 64 bit integer values all parse with int()
+print(int("-9223372036854775807"))
+print(int("-9223372036854775808"))
+print(int("9223372036854775807"))
+
+# Test that the most negative 64 bit integer can be formed via arithmetic
+print(-9223372036854775807-1)