Compiler/TMS320F28379D: Conversion loses integer precision warning

This is a violation of MISRA rule 10.1 ...

Rule 10.1 (required)    The value of an expression of integer type shall not
                        be implicitly converted to a different underlying type
                        if:
                        a) it is not a conversion to a wider integer type of
                           the same signedness, or
                        b) the expression is complex, or
                        c) the expression is not constant and is a function
                           argument, or
                        d) the expression is not constant and is a return
                           expression.

So I tried adding the build option --check_misra=10.1.  I found that, if variables a and b are local to the function, and written exactly as you did ...

Carl Friess said:

uint32_t a = 0;
uint16_t b = a;

then no diagnostic is issued.  If the variables are global, or the assignments are written separately, then you see a diagnostic.  That's wrong, so I filed CODEGEN-4712 in the SDOWP system to have this investigated. You are welcome to follow it with the SDOWP link below in my signature.

When you do see a diagnostic, it occurs for both lines ...

% cl2000 --verbose_diagnostics --check_misra=10.1 file.c
"file.c", line 11: warning: (MISRA-C:2004 10.1/R) The value of an expression of
          integer type shall not be implicitly converted to a different
          underlying type if it is not a conversion to a wider integer type of
          the same signedness
     a = 0;
         ^

"file.c", line 12: warning: (MISRA-C:2004 10.1/R) The value of an expression of
          integer type shall not be implicitly converted to a different
          underlying type if it is not a conversion to a wider integer type of
          the same signedness
     b = a;
         ^

You can avoid the first diagnostic by adding the suffix u, which changes the type of the integer constant 0 to unsigned.

a = 0u;

Thanks and regards,

-George