refactor: change type of linenr_T from long to int32_t

The size of long varies depending on architecture, in contrast to the
MAXLNUM constant which sets the maximum allowable number of lines to
2^32-1. This discrepancy may lead to hard to detect bugs, for example
https://github.com/neovim/neovim/issues/18454. Setting linenr_T to a
fix maximum size of 2^32-1 will prevent this type of errors in the
future.

Also change the variables `amount` and `amount_after` to be linenr_T
since they're referring to "the line number difference" between two
texts.

1 files changed, 16 insertions, 0 deletions

diff --git a/src/nvim/charset.c b/src/nvim/charset.c
index e20c0e3f3f..9bc0bef446 100644
--- a/src/nvim/charset.c
+++ b/src/nvim/charset.c
@@ -1392,6 +1392,22 @@ long getdigits_long(char_u **pp, bool strict, long def)
   return (long)number;
 }
 
+/// Gets a int32_t number from a string.
+///
+/// @see getdigits
+int32_t getdigits_int32(char **pp, bool strict, long def)
+{
+  intmax_t number = getdigits((char_u **)pp, strict, def);
+#if SIZEOF_INTMAX_T > SIZEOF_INT32_T
+  if (strict) {
+    assert(number >= INT32_MIN && number <= INT32_MAX);
+  } else if (!(number >= INT32_MIN && number <= INT32_MAX)) {
+    return (int32_t)def;
+  }
+#endif
+  return (int32_t)number;
+}
+
 /// Check that "lbuf" is empty or only contains blanks.
 ///
 /// @param  lbuf  line buffer to check