rn-128: add article about printf() format specifiers

Author: chriscool

rev_news/drafts/edition-128.md

@@ -25,9 +25,63 @@ This edition covers what happened during the months of September and October 202
 ### Reviews
 -->
 
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+
 ### Support
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+
++ [[Change] Git build issue on NonStop](https://lore.kernel.org/git/[email protected]/)
+
+  Randall S. Becker reported on the mailing list that CI tests on the
+  NonStop x86 platform were broken after the `uintptr_t` type started
+  to be used in [clar](https://github.com/clar-test/clar) tests when
+  displaying error messages in test failures (when pointer comparisons
+  fail).
+
+  Peff, alias Jeff King, replied to Randall that `uintptr_t` was
+  already used in many places in the regular code, and guessed the
+  issue might come from how clar defined that type. He noted though
+  that the line in the clar test where `uintptr_t` appeared also
+  contained `PRIxPTR` which is a macro that is not used in the regular
+  code. So he wondered if just replacing that macro with `PRIuMAX`
+  (which is often used) would be enough to fix the issue.
+
+  `PRIxPTR`, `PRIuMAX` and similar macros are format specifier macros
+  from the C standard library (defined in `<inttypes.h>`) that provide
+  portable ways to print integer types using functions like `printf()`
+  across different platforms. They are all named in the same way, with
+  `PRI` meaning `printf`, the next letter indicating the format, like
+  `x` for hexadecimal and `u` for unsigned decimal, and the last part
+  indicating the type, like `PTR` for pointer-sized integers, `MAX`
+  for maximum-width integers, `64` for 64-bit, etc.
+
+  Randall replied to Peff that replacing `PRIxPTR` with `PRIuMAX`
+  would work, and that he was going to try it.
+
+  Patrick Steinhardt also replied to Randall and Peff saying it would
+  work, and asked Peff if he wanted to send that change.
+
+  Peff replied to Patrick that he'd be happy if Patrick sent the
+  change, but noted that using `PRIxMAX` might be better than
+  `PRIuMAX` as the code wanted to print hexadecimal values.
+
+  Patrick then reported to Peff that Peff's suggestion to use the
+  `PRIxMAX` or `PRIuMAX` format specifier macros didn't work on 32 bit
+  systems, because casting a pointer to an integer of different size
+  (the pointer is 32 bits, but `uintmax_t` is 64 bits) fails.
+
+  Patrick proposed using `%p` as a format specifier saying it might be
+  a better trade-off. The downside was that the output format would be
+  unpredictable across platforms as `%p` doesn't have a standardized
+  output format. So tests that validated the exact error message
+  format would have to be dropped. But at least `%p` would work
+  everywhere and produce stable output.
+
+  Junio Hamano, the Git maintainer, agreed with Patrick that `%p` was
+  "the most appropriate solution".
+
+  Randall then confirmed that `%p` worked on NonStop x86 even if the
+  man pages warned to the contrary.
+
+  The `%p` solution was eventually merged to the 'master' branch.
 
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