From fdbc09e2a53281b8dda7c48676dcf695a79ba373 Mon Sep 17 00:00:00 2001
From: Andrew Tridgell <tridge@samba.org>
Date: Wed, 28 Aug 2013 18:31:27 +1000
Subject: [PATCH] avoid counters going above limit in INCREMENT()

when using INCREMENT() the counter would temporarily read equal to
limit, which could cause an issue if the task is preempted.

(this macro should be in a common header, though which header?)
---
 src/drivers/airspeed/airspeed.h | 2 +-
 src/drivers/bma180/bma180.cpp   | 2 +-
 src/drivers/hmc5883/hmc5883.cpp | 2 +-
 src/drivers/l3gd20/l3gd20.cpp   | 2 +-
 src/drivers/lsm303d/lsm303d.cpp | 2 +-
 src/drivers/mb12xx/mb12xx.cpp   | 2 +-
 src/drivers/ms5611/ms5611.cpp   | 2 +-
 7 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/src/drivers/airspeed/airspeed.h b/src/drivers/airspeed/airspeed.h
index 89dfb22d70..b87494b40f 100644
--- a/src/drivers/airspeed/airspeed.h
+++ b/src/drivers/airspeed/airspeed.h
@@ -165,5 +165,5 @@ protected:
 };
 
 /* helper macro for handling report buffer indices */
-#define INCREMENT(_x, _lim)	do { _x++; if (_x >= _lim) _x = 0; } while(0)
+#define INCREMENT(_x, _lim)	do { __typeof__(_x) _tmp = _x+1; if (_tmp >= _lim) _tmp = 0; _x = _tmp; } while(0)
 
diff --git a/src/drivers/bma180/bma180.cpp b/src/drivers/bma180/bma180.cpp
index cfb6256704..079b5d21cb 100644
--- a/src/drivers/bma180/bma180.cpp
+++ b/src/drivers/bma180/bma180.cpp
@@ -234,7 +234,7 @@ private:
 };
 
 /* helper macro for handling report buffer indices */
-#define INCREMENT(_x, _lim)	do { _x++; if (_x >= _lim) _x = 0; } while(0)
+#define INCREMENT(_x, _lim)	do { __typeof__(_x) _tmp = _x+1; if (_tmp >= _lim) _tmp = 0; _x = _tmp; } while(0)
 
 
 BMA180::BMA180(int bus, spi_dev_e device) :
diff --git a/src/drivers/hmc5883/hmc5883.cpp b/src/drivers/hmc5883/hmc5883.cpp
index 1a337ca3a8..a5229b2371 100644
--- a/src/drivers/hmc5883/hmc5883.cpp
+++ b/src/drivers/hmc5883/hmc5883.cpp
@@ -311,7 +311,7 @@ private:
 };
 
 /* helper macro for handling report buffer indices */
-#define INCREMENT(_x, _lim)	do { _x++; if (_x >= _lim) _x = 0; } while(0)
+#define INCREMENT(_x, _lim)	do { __typeof__(_x) _tmp = _x+1; if (_tmp >= _lim) _tmp = 0; _x = _tmp; } while(0)
 
 /*
  * Driver 'main' command.
diff --git a/src/drivers/l3gd20/l3gd20.cpp b/src/drivers/l3gd20/l3gd20.cpp
index 5e0a2119a1..e6d765e13a 100644
--- a/src/drivers/l3gd20/l3gd20.cpp
+++ b/src/drivers/l3gd20/l3gd20.cpp
@@ -300,7 +300,7 @@ private:
 };
 
 /* helper macro for handling report buffer indices */
-#define INCREMENT(_x, _lim)	do { _x++; if (_x >= _lim) _x = 0; } while(0)
+#define INCREMENT(_x, _lim)	do { __typeof__(_x) _tmp = _x+1; if (_tmp >= _lim) _tmp = 0; _x = _tmp; } while(0)
 
 
 L3GD20::L3GD20(int bus, const char* path, spi_dev_e device) :
diff --git a/src/drivers/lsm303d/lsm303d.cpp b/src/drivers/lsm303d/lsm303d.cpp
index cf5f8d94ce..05d6f1881d 100644
--- a/src/drivers/lsm303d/lsm303d.cpp
+++ b/src/drivers/lsm303d/lsm303d.cpp
@@ -421,7 +421,7 @@ private:
 
 
 /* helper macro for handling report buffer indices */
-#define INCREMENT(_x, _lim)	do { _x++; if (_x >= _lim) _x = 0; } while(0)
+#define INCREMENT(_x, _lim)	do { __typeof__(_x) _tmp = _x+1; if (_tmp >= _lim) _tmp = 0; _x = _tmp; } while(0)
 
 
 LSM303D::LSM303D(int bus, const char* path, spi_dev_e device) :
diff --git a/src/drivers/mb12xx/mb12xx.cpp b/src/drivers/mb12xx/mb12xx.cpp
index c5f49fb36e..f834169935 100644
--- a/src/drivers/mb12xx/mb12xx.cpp
+++ b/src/drivers/mb12xx/mb12xx.cpp
@@ -184,7 +184,7 @@ private:
 };
 
 /* helper macro for handling report buffer indices */
-#define INCREMENT(_x, _lim)	do { _x++; if (_x >= _lim) _x = 0; } while(0)
+#define INCREMENT(_x, _lim)	do { __typeof__(_x) _tmp = _x+1; if (_tmp >= _lim) _tmp = 0; _x = _tmp; } while(0)
 
 /*
  * Driver 'main' command.
diff --git a/src/drivers/ms5611/ms5611.cpp b/src/drivers/ms5611/ms5611.cpp
index b572e042c6..4e43f19c5d 100644
--- a/src/drivers/ms5611/ms5611.cpp
+++ b/src/drivers/ms5611/ms5611.cpp
@@ -77,7 +77,7 @@ static const int ERROR = -1;
 #endif
 
 /* helper macro for handling report buffer indices */
-#define INCREMENT(_x, _lim)	do { _x++; if (_x >= _lim) _x = 0; } while(0)
+#define INCREMENT(_x, _lim)	do { __typeof__(_x) _tmp = _x+1; if (_tmp >= _lim) _tmp = 0; _x = _tmp; } while(0)
 
 /* helper macro for arithmetic - returns the square of the argument */
 #define POW2(_x)		((_x) * (_x))