fix: build the FreeRTOS pack at any tick rate (#756)

* fix: build the FreeRTOS pack at any tick rate

The sysUpTime adapter carried a static assert requiring a 64-bit TickType_t,
or a 32-bit one whose configTICK_RATE_HZ divides 100. The umbrella target
compiles that translation unit unconditionally, so an ordinary 1000 Hz
configuration cost the integrator the whole pack, the mutex included.

Remove the assert. The adapter builds everywhere and its header states where
the value wraps early; #755 tracks removing the limit itself.

* docs: make the FreeRTOS uptime rollover period rate-specific

Author: DavidCozens

Core/Interface/SolidSyslogMetaSd.h

@@ -18,8 +18,10 @@ SOLIDSYSLOG_EXTERN_C_BEGIN
     struct SolidSyslogAtomicCounter;
     struct SolidSyslogStructuredData;
 
-    /** Returns system uptime in hundredths of a second (RFC 3418 TimeTicks),
-     *  wrapping on overflow. Feeds the meta element's sysUpTime PARAM. */
+    /** Returns system uptime in hundredths of a second (RFC 3418 TimeTicks):
+     *  monotonic, and wrapping to zero only at 2^32 hundredths. A source counter
+     *  that rolls over sooner must carry the phase across, or the value steps
+     *  backwards mid-range. Feeds the meta element's sysUpTime PARAM. */
     typedef uint32_t (*SolidSyslogSysUpTimeFunction)(void);
 
     /** Wiring for the "meta" SD-ELEMENT (RFC 5424 §7.3). Whatever is provided

Platform/FreeRtos/Interface/SolidSyslogFreeRtosSysUpTime.h

@@ -11,15 +11,11 @@
 SOLIDSYSLOG_EXTERN_C_BEGIN
 
     /** Hundredths of a second of uptime from xTaskGetTickCount, for the meta-SD
-     *  sysUpTime field — a faithful RFC 3418 modulo-2^32 TimeTicks counter. A
-     *  compile-time guard rejects tick configurations whose counter would wrap
-     *  non-continuously mod 2^32. Supported envelope: a 64-bit TickType_t at any
-     *  tick rate (faithful over any realistic uptime — its wrap is millions of
-     *  years out), or a 32-bit TickType_t whose configTICK_RATE_HZ divides 100
-     *  (100/50/25/20/10/5/4/2/1 Hz — faithful for the counter's whole lifetime).
-     *  A 16-bit tick counter, or a 32-bit rate that does not divide 100
-     *  (including any rate above 100 Hz), fails to build (widen the tick type,
-     *  pick a dividing rate, or supply your own SolidSyslogSysUpTimeFunction). */
+     *  sysUpTime field. Meets the SolidSyslogSysUpTimeFunction contract for a
+     *  64-bit TickType_t at any tick rate, and for a 32-bit one whose
+     *  configTICK_RATE_HZ divides 100. Elsewhere — the 1000 Hz default among
+     *  them — the value wraps to zero early, so supply your own
+     *  SolidSyslogSysUpTimeFunction where uptime matters. */
     uint32_t SolidSyslogFreeRtos_GetSysUpTime(void);
 
 SOLIDSYSLOG_EXTERN_C_END

Platform/FreeRtos/Source/SolidSyslogFreeRtosSysUpTime.c

@@ -3,37 +3,17 @@
 #include "FreeRTOS.h"
 #include "task.h"
 
-#include "SolidSyslogMacros.h"
-
 enum
 {
     HUNDREDTHS_PER_SECOND = 100
 };
 
-/* The uint32 result is a faithful RFC 3418 modulo-2^32 hundredths counter only
- * while every FreeRTOS tick-counter wrap stays phase-continuous mod 2^32. That
- * offset is zero for a 64-bit TickType_t at any tick rate (its wrap is millions
- * of years out, beyond any realistic uptime), or a 32-bit TickType_t whose
- * configTICK_RATE_HZ divides 100 (100/50/25/20/10/5/4/2/1 Hz) — then each tick
- * is an exact whole number of hundredths and the wrap lands cleanly. A 16-bit
- * tick counter, or a 32-bit rate that does not divide 100 (including any rate
- * above 100 Hz), injects a backwards jump at the wrap — refuse to build it
- * rather than ship a subtly wrong value. An integrator outside this envelope
- * should widen TickType_t (configTICK_TYPE_WIDTH_IN_BITS = TICK_TYPE_WIDTH_64_BITS),
- * pick a rate that divides 100, or supply their own SolidSyslogSysUpTimeFunction. */
-SOLIDSYSLOG_STATIC_ASSERT(
-    (sizeof(TickType_t) >= 8U) || ((sizeof(TickType_t) >= 4U) && ((HUNDREDTHS_PER_SECOND % configTICK_RATE_HZ) == 0U)),
-    "SolidSyslogFreeRtosSysUpTime needs a 64-bit TickType_t (any tick rate), or a 32-bit TickType_t "
-    "with a configTICK_RATE_HZ that divides 100 (100/50/25/20/10/5/4/2/1 Hz), for a faithful RFC "
-    "3418 TimeTicks; widen the tick type, use a dividing rate, or supply your own "
-    "SolidSyslogSysUpTimeFunction."
-);
-
 uint32_t SolidSyslogFreeRtos_GetSysUpTime(void)
 {
     /* Divide the tick count down before scaling by 100 so the intermediate
      * cannot overflow even a 64-bit TickType_t; the whole/remainder split is
-     * exact floor division, and the uint32 cast wraps per RFC 3418 TimeTicks. */
+     * exact floor division, and the uint32 cast wraps per RFC 3418 TimeTicks.
+     * The header states which tick configurations wrap early. */
     uint64_t ticks = (uint64_t) xTaskGetTickCount();
     uint64_t wholeSecondHundredths = (ticks / configTICK_RATE_HZ) * HUNDREDTHS_PER_SECOND;
     uint64_t subSecondHundredths = ((ticks % configTICK_RATE_HZ) * HUNDREDTHS_PER_SECOND) / configTICK_RATE_HZ;

docs/platforms/freertos/index.md

@@ -32,3 +32,16 @@ nothing at run time and cannot fail for want of heap.
 The sysUpTime callback reports kernel ticks since boot. It is not wall-clock
 time and carries no timezone or synchronisation quality — the clock callback is
 a separate injection point.
+
+> [!WARNING]
+> `SolidSyslogFreeRtos_GetSysUpTime` meets the
+> [sysUpTime contract](../../api/SolidSyslogMetaSd_8h.md) for a 64-bit
+> `TickType_t` at any tick rate, and for a 32-bit one whose `configTICK_RATE_HZ`
+> divides 100. At every other rate the tick counter rolls over before 2^32
+> hundredths do, and the reported uptime loses phase there and returns to zero:
+> after 2^32 / `configTICK_RATE_HZ` seconds rather than RFC 3418's 497 days, so
+> roughly 50 days at the 1000 Hz FreeRTOS default and sooner as the rate rises.
+> Supply your own `SolidSyslogSysUpTimeFunction` from a time source you already
+> have, or move to a dividing rate or a 64-bit tick type. Converting correctly
+> at any tick rate is tracked as
+> [#755](https://github.com/cososo-ltd/solid-syslog/issues/755).

misra_suppressions.txt

@@ -173,7 +173,7 @@ misra-c2012-5.7:Core/Source/SolidSyslogCircularBuffer.c:21
 misra-c2012-5.7:Core/Source/SolidSyslogCrc16.c:12
 misra-c2012-5.7:Core/Source/SolidSyslogCrc16Policy.c:10
 misra-c2012-5.7:Core/Source/SolidSyslogOriginSdPrivate.h:13
-misra-c2012-5.7:Platform/FreeRtos/Source/SolidSyslogFreeRtosSysUpTime.c:9
+misra-c2012-5.7:Platform/FreeRtos/Source/SolidSyslogFreeRtosSysUpTime.c:7
 misra-c2012-5.7:Platform/Posix/Source/SolidSyslogPosixHostname.c:10
 misra-c2012-5.7:Platform/Posix/Source/SolidSyslogPosixMessageQueueBuffer.c:25
 misra-c2012-5.7:Platform/Posix/Source/SolidSyslogPosixMessageQueueBufferPrivate.h:17