From 4f22de2333bcd9cfd603c144dd037358fc3c9d5f Mon Sep 17 00:00:00 2001
From: Yuri D'Elia <wavexx@thregr.org>
Date: Sat, 6 Aug 2022 23:15:46 +0200
Subject: [PATCH] Do *not* shorten the current command in printer_smodel_check

printer_smodel_check was incorrectly substituting the final " with a
null in the command to simplify the model string comparison, but in
doing so was also corrupting the next pop from the cmdqueue.

We can modify the current strchr_pointer as long as we *don't* change
it's length. This can cause an incorrect extra read from the queue,
resulting in the last command to be completely ignored.
---
 Firmware/util.cpp | 7 +++----
 Firmware/util.h   | 2 +-
 2 files changed, 4 insertions(+), 5 deletions(-)

diff --git a/Firmware/util.cpp b/Firmware/util.cpp
index 7b192b8c3..3d789e08f 100644
--- a/Firmware/util.cpp
+++ b/Firmware/util.cpp
@@ -431,7 +431,7 @@ lcd_update_enable(true);           // display / status-line recovery
 #define GCODE_DELIMITER '"'
 #define ELLIPSIS "..."
 
-char* code_string(char* pStr,size_t* nLength)
+char* code_string(const char* pStr,size_t* nLength)
 {
 char* pStrBegin;
 char* pStrEnd;
@@ -444,11 +444,10 @@ pStrEnd=strchr(pStrBegin,GCODE_DELIMITER);
 if(!pStrEnd)
      return(NULL);
 *nLength=pStrEnd-pStrBegin;
-pStrBegin[*nLength] = '\0';
 return pStrBegin;
 }
 
-void printer_smodel_check(char* pStrPos)
+void printer_smodel_check(const char* pStrPos)
 {
 char* pResult;
 size_t nLength,nPrinterNameLength;
@@ -458,7 +457,7 @@ pResult = code_string(pStrPos,&nLength);
 
 if(pResult != NULL && nLength == nPrinterNameLength) {
      // Only compare them if the lengths match
-     if (strcmp_P(pResult, sPrinterName) == 0) return;
+     if (strncmp_P(pResult, sPrinterName, nLength) == 0) return;
 }
 
 switch(oCheckModel)
diff --git a/Firmware/util.h b/Firmware/util.h
index 6d34aa081..7533429e2 100644
--- a/Firmware/util.h
+++ b/Firmware/util.h
@@ -104,7 +104,7 @@ extern ClCheckGcode oCheckGcode;
 void fCheckModeInit();
 void nozzle_diameter_check(uint16_t nDiameter);
 void printer_model_check(uint16_t nPrinterModel);
-void printer_smodel_check(char* pStrPos);
+void printer_smodel_check(const char* pStrPos);
 void fw_version_check(const char *pVersion);
 void gcode_level_check(uint16_t nGcodeLevel);