%o and %x can now format signed integers
Optionally treat integers as signed numbers with %o and %x format specifiers, instead of treating them as a machine-dependent two’s complement representation. This option is more machine-independent, allows formats like "#x%x" to be useful for reading later, and is better-insulated for future changes involving bignums. Setting the new variable ‘binary-as-unsigned’ to nil enables the new behavior (Bug#32252). This is a simplified version of the change proposed in: https://lists.gnu.org/r/emacs-devel/2018-07/msg00763.html I simplified that proposal by omitting bitwidth modifiers, as I could not find an any example uses in the Emacs source code that needed them and doing them correctly would have been quite a bit more work for apparently little benefit. * doc/lispref/strings.texi (Formatting Strings): Document that %x and %o format negative integers in a platform-dependent way. Also, document how to format numbers so that the same values can be read back in. * etc/NEWS: Document the change. * src/editfns.c (styled_format): Treat integers as signed numbers even with %o and %x, if binary-as-unsigned is nil. Support the + and space flags with %o and %x, since they’re about signs. (syms_of_editfns): New variable binary-as-unsigned. * test/src/editfns-tests.el (read-large-integer): Test that maximal integers can be read after printing with all integer formats, if binary-as-unsigned is nil.
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