MATLAB: Polyspace MISRA C 2012 Rules 8.1 and 17.3 seem to be disabled even when selected

Polyspace Code Prover

I enabled rules MISRA C 2012 Rules 8.1 and 17.3 in my Polyspace Code Prover Project Configuration. However, the generated report indicates that these rules are disabled.
Guideline Description Mode Enabled 
8.1 Types shall be explicitly specified. required FALSE 
17.3 A function shall not be declared implicitly. mandatory FALSE
I tried the same rules with and without option "Use Generated Code Requirements", but got the same result.

Best Answer

These two MISRA rules are dedicated to ANSI C90 Standard only. By default, when you launch Polyspace Code Prover, the project is ANSI C99 Standard compliant, and not C90. As a result, these two rules get disabled during verification.
In Polyspace R2018a and earlier, you can enable them by selecting "Respect C90 Standard" under "Target & Compiler" section of the project configuration.
In Polyspace R2018b and newer, you can enable the C90 standard by switching the "C Standard Version" under the "Target & Compiler" section to C90.
NOTE: This may have some side-effects because the code will be required to be C90 standard compliant.
Below are the documentation references for the rules 8.1 and 17.3 to show that they are C90 MISRA 2012 rules:
http://www.mathworks.com/help/codeprover/ref/misrac2012rule8.1.html
http://www.mathworks.com/help/codeprover/ref/misrac2012rule17.3.html
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