From ca5df0b598fe8022be5b01f8ff01fe2d5f7c622e Mon Sep 17 00:00:00 2001
From: PhysicistJohn <54456354+PhysicistJohn@users.noreply.github.com>
Date: Tue, 14 Jul 2026 11:30:00 -0700
Subject: [PATCH] fix: normalize exact powers in scientific output

The compact scientific formatter emits its leading digit by adding the
normalized integer mantissa to '0'.  Its upper normalization loop stops at
exactly 10, however, so powers of ten use ':' (the character after '9') as
their leading digit.  For example, -100.0 becomes -:.000000e+01.

Keep the normalized mantissa below 10.  This preserves surrounding values
and renders exact powers with a valid leading digit and adjusted exponent.
---
 chprintf.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/chprintf.c b/chprintf.c
index 07f52f4..6bba7fe 100644
--- a/chprintf.c
+++ b/chprintf.c
@@ -231,7 +231,7 @@ static char *etoa(char *p, float num, uint32_t precision) {
   int exp = 0;
   if (num == 0) { *p++ = '0'; return p; }
   while (num < 10) { num *= 10.0; exp--; }
-  while (num > 10) { num /= 10.0; exp++; }
+  while (num >= 10) { num /= 10.0; exp++; }
   *p++ = ((int)num) + '0'; num *=10.0;
   *p++ = '.';
   if (precision == 0) precision = 6;