(format "%d" F) now truncates floating F

Problem reported by Paul Pogonyshev (Bug#31938).
* src/editfns.c: Include math.h, for trunc.
(styled_format): For %d, truncate floating-point numbers and
convert -0 to 0, going back to how Emacs 26 did things.
* doc/lispref/strings.texi (Formatting Strings):
Document behavior of %o, %d, %x, %X on floating-point numbers.
* src/floatfns.c (trunc) [!HAVE_TRUNC]: Rename from emacs_trunc
and make it an extern function, so that editfns.c can use it.
All callers changed.
* test/src/editfns-tests.el (format-%d-float): New test.

1 files changed, 8 insertions, 3 deletions

diff --git a/doc/lispref/strings.texi b/doc/lispref/strings.texi
index 70ba1aa613e..026ba749cbd 100644
--- a/doc/lispref/strings.texi
+++ b/doc/lispref/strings.texi
@@ -922,18 +922,23 @@ Functions}).  Thus, strings are enclosed in @samp{"} characters, and
 @item %o
 @cindex integer to octal
 Replace the specification with the base-eight representation of an
-unsigned integer.
+unsigned integer.  The object can also be a nonnegative floating-point
+number that is formatted as an integer, dropping any fraction, if the
+integer does not exceed machine limits.
 
 @item %d
 Replace the specification with the base-ten representation of a signed
-integer.
+integer.  The object can also be a floating-point number that is
+formatted as an integer, dropping any fraction.
 
 @item %x
 @itemx %X
 @cindex integer to hexadecimal
 Replace the specification with the base-sixteen representation of an
 unsigned integer.  @samp{%x} uses lower case and @samp{%X} uses upper
-case.
+case.  The object can also be a nonnegative floating-point number that
+is formatted as an integer, dropping any fraction, if the integer does
+not exceed machine limits.
 
 @item %c
 Replace the specification with the character which is the value given.