An introduction to the SuperTest MISRA suites

The SuperTest MISRA suites are created to verify the conformance of MISRA checking software. The aim of a, so-called, MISRA checker is to check application software for its compliance with the MISRA guidelines.  The SuperTest MISRA suites in turn verify that such a MISRA checker generates the right diagnostics and not too many false positives or false negatives.

The MISRA suites contain two types of tests: those which a name starting with an 'x', and those which a name that starts with a 't'.

T-tests

The so-called t-tests are fully conforming with the MISRA guidelines and should not trigger any diagnostics in the MISRA checking software. This is an example of a t-test:

 /*

  * Test for MISRA-C:2004 Rule 4.2:

  *     Trigraphs shall not be used

  */

 typedef signed int int32_t;

 static int32_t fun (void);

 static int32_t fun (void) {

     char r[50] = "OK: ??? ??.??+??~??^"; /* Compliant */

     return (r[0] != 'O') ? (int32_t)1 : (int32_t)0;

 }

 int32_t main (void) {

     return fun ();

 }

In this test, the string that initializes the variable r[50] contains a number of character sequences that look like trigraph sequences, which the MISRA guidelines do not allow, but are not trigraphs. Hence, this code is compliant with MISRA Rule 4.2. No diagnostic should be given. The code is also constructed so that no other MISRA rules are violated.

X-tests

The x-tests contain a violation of one of the MISRA rules. When passed to a MISRA checker, they should trigger a diagnostic for a specific rule. Here is an example of an x-test that violates Rule 5.4, which requires that tags are unique.

 /*

  * Test for MISRA-C:2004 Rule 5.4:

  *     A tag name shall be a unique identifier

  * 

  * Notes on test:

  * Check that the following code violates MISRA Rule 5.4

  */

 typedef unsigned short uint16_t;

 typedef signed int int32_t;

 typedef unsigned int uint32_t;

 int32_t main (void) {

     uint32_t aval;

     { 

         enum thetag { x, y, z };

         enum thetag ty = y;

         aval = (ty < x) ? (int32_t)1U : (int32_t)0U;

     } 

     { 

         struct thetag {   /* Not compliant */

             uint16_t a;

             uint16_t b;

         } str = {3U, 4U};

         aval += str.a;

     } 

     return (aval != 3U) ? (int32_t)1 : (int32_t)0;

 }

Note that this x-test is perfectly fine C90 code. C90 allows the reuse of thetag in different scopes. But MISRA does not.

A big effort has been put into making the x-tests as specific as possible, so that they contain only one rule violation, and at the same time keep them concise and understandable. This is not always possible. Sometimes rules partially overlap and an additional diagnostic is triggered.

Undecidable Rules

Some of the MISRA rules are what is called undecidable.  This means that for complex examples of such code, a MISRA checker may not be able to follow the control and data flow with sufficiently detail to decide if a rule is violated or not. For such rules, there are often 'trivial' cases for which a MISRA checker is expected to give a diagnostic. We have tried to include such trivial cases in the suites as well. We have also tried to include more complex cases that are decidable with some effort. The following is an example of a t-test for an undecidable rule, so it should not give a diagnostic:

 /*

  * Test for MISRA-C:2004 Rule 17.3:

  *     >, >=, <, <= shall not be applied to pointer

  *     types except where they point to the same array

  * 

  * Notes on test:

  * Check that the code does not violate MISRA Rule 17.3

  */

 typedef signed int int32_t;

 int32_t main (void) {

     int32_t a[] = {1, 2, 3};

     int32_t *pa = &a[1];

     int32_t r = 9;

     if (&a[2] > pa) {   /* Compliant */

         r = 6;

     } 

     return r - 6;

 }

To verify that the pointer comparison is compliant, requires that a MISRA checker applies non-trivial data flow analysis to the code. If the MISRA checker cannot do that, it might decide to play it safe and generate a false positive: an incorrect diagnostic for a (possible) rule violation. MISRA checker may offer options to suppress false positives.

The MISRA test suite comes in several flavors. By means of (advisory) Rule 6.3, MISRA forces application developers to choose a data model and express that choice in the primitive types used for arithmetic. This can be seen in the examples above, which use the 32-bit integer type "int32_t".

The MISRA suites are supplied both in a generic form and in a form that is specific for a data model. The examples above are all for a specific data model. In the generic form, the previous example looks like this:

 int main (void) {

     int a[] = {1, 2, 3};

     int *pa = &a[1];

     int r = 9;

     if (&a[2] > pa) {   /* Compliant */

         r = 6;

     }

     return r - 6;

 }

In this form, one should tell the MISRA checker that it should ignore Rule 6.3.

Solid Sands can also provide additional instances of the MISRA suites that are specific for another data model, if needed.


Extracts of the MISRA C guidelines used with permission of HORIBA MIRA LIMITED. MISRA is a registered trademark of HORIBA MIRA LIMITED.

For example test code:
(c) Copyright 2015-2017 by Solid Sands B.V.,   
Amsterdam, the Netherlands. All rights reserved.
Subject to conditions in the RESTRICTIONS file.
Copyright (c) 2015 Analog Devices, Inc.  All rights reserved.

(c) Copyright 2017 by Solid Sands B.V., Amsterdam, the Netherlands
SuperTest™ is a trademark of Solid Sands B.V., Amsterdam, The Netherlands.


Related


The Benefits of C and C++ Compiler Qualification

In embedded application development, the correct operation of the compilation toolset is critical to the functional safety of the application. Two options are available to build trust in the corre...

8 Ways to Improve Harness Manufacturing

Harness manufacturing is a low margin business where quality, accuracy, and speed are essential to success. It can benefit from a full, automated and digitally continuous flow from product design to h...

General principles of PCBs design

How to design PCBs correctly, to reach boards which are cost-effective to produce and to populate? Which are the most important PCB design principles? What about production technology of PCB? We have ...

The Next Level of Embedded Software Development

With the rapid expansion of complex technology into everyday life, the importance of software is growing exponentially. This complimentary webinar presented by Siemens PLM Software will show how emb...

Embedded Software for Safety Critical Applications

Production code generation with Model-Based Design has replaced document-based development and manual coding in various domains in automotive, industrial automation, aerospace and medical. Safety-rela...

Coding safe and secure applications

The debate about safety and security concerns in high integrity software applications is a hot topic of discussion in modern software management. The need to address these concerns is present in e...

Best practices for static analysis tools

This paper reviews a number of the growing complexities that embedded software development teams are facing, including the proliferation of third-party code, increased pressures to develop secure ...


Making your device secure

The internet of things is faced with a major security challenge. Compared to traditional, often unconnected embedded systems, the nature of IoT devices radically increases the risk of attack not just ...

 


Dirk Giesen describes the Parasoft tool suite for Embedded Software Development

Are you responsible for embedded software development in your organization? Your goal should be to create safe, secure, and reliable software. To make sure your device will work properly, deploy Paras...


Ross Sabolik of Silicon Labs talks about advanced Power over Ethernet

In this video Ross Sabolik of Silicon Labs talks about smart  Power over Ethernet systems with Alix Paultre at their APEC exhibit in San ANtonio, Texas. As PoE migrates to higher power levels and...


Dialog Semi walks through their latest IC solutions for battery chargers

In this video an engineer from Dialog Semiconductor walks us through their latest ICs for battery chargers at APEC 2018. Dialog's Qualcomm Quick Charge adapter solutions offer high efficiency to e...


Steve Allen of pSemi explains their latest LED driver solution

Steve Allen of pSemi explains their latest LED boost product based on Arctic Sand's two-stage architecture. Their PE23300 has a charge-pump, switched-capacitor architecture that offloads most of t...


Teledyne describes their latest 12-bit Wavepro HD oscilloscope

In this video Teledyne LeCroy describes their latest Wavepro HD oscilloscope to Alix Paultre of Power Electronics News at the company's launch event. The WavePro HD high-definition oscilloscope de...


Dialog Semi walks through their latest IC solutions for battery chargers

In this video an engineer from Dialog Semiconductor walks us through their latest ICs for battery chargers at APEC 2018. Dialog's Qualcomm Quick Charge adapter solutions offer high efficiency to e...


ROHM explains their latest wireless battery charger solution kit

In this video an engineer from ROHM goes over their latest wireless power development kit, co-developed with Würth for embedded development. The kit provides a complete wireless power transfer sy...


Tektronix describes their latest mixed-signal oscilloscope

In this video Tektronix explains the features in their latest 5 Series MSO Mixed Signal Oscilloscope. Features include an innovative pinch-swipe-zoom touchscreen user interface, a large high-definitio...


AVX shows a supercapacitor demonstrator at APEC

In this video Eric from AVX explains their supercapacitor demonstrator box at APEC 2018 in San Antonio, Texas. The box shows how a 5V 2.5-farad supercapacitor can quickly charge up using harvested ene...


OnSemi explains their latest passive smart wireless sensor for industrial applications

In this video On Semiconductor explains their latest wireless sensor for hazardous environments at APEC in San Antonio, Texas. Intended for applications like high-voltage power cabinets and other plac...


TI demonstrates an improved gaming power system at Embedded World

In this video Texas Instruments' explains Significant reduction in ripple, which results in improved reliability and increased design margins, among other advantages. Another benefit that improve...


Infineon explains their latest motor drive technology at APEC 2018

In this video Infineon demonstrates new gate drivers using their LS-SOI technology at APEC 2018. In the demo Victorus, an Infineon application engineer, shows in real time how much better thermal the ...


STMicro goes over their latest wireless-enabled microcontroller for the IoT

In this video STMicroelectronics goes over their latest wireless-enabled STM32WB microcontroller for the IoT and intelligent devices in several live connectivity demonstrations at Embedded World 2018....