illumos gate

I wonder if we can just pad out the lint output to be more informative, or whether to be more selective about what warnings to print. I already suppressed the one about grave accents being deprecated.

This one does seem a worthwhile warning, just hard to interpret - the shell docbook that's still in the gate tree says:

Avoid string to number and/or number to string conversions in arithmetic expressions to avoid
performance degradation and rounding errors.

Example 6. (( x=$x*2 )) vs. (( x=x*2 ))

float x
...
(( x=$x*2 ))
will convert the variable "x" (stored in the machine's native |long double| datatype) to a string value in base10 format,
apply pattern expansion (globbing), then insert this string into the arithmetic expressions and parse the value which
converts it into the internal |long double| datatype format again. This is both slow and generates rounding errors when
converting the floating-point value between the internal base2 and the base10 representation of the string.

The correct usage would be:

float x
...
(( x=x*2 ))
e.g. omit the '$' because it's (at least) redundant within arithmetic expressions.

I wasn't asking to get rid of the warning, mainly to make sure when we have this kind of warning to explain what's going on in more detail. The reason this isn't immediately obvious is that special variables (like the case where I hit this in #13601 require you to still use a leading $. I think error messages when there's additional context about how to correctly fix it will help folks out a lot.

With the change in the associated Gerrit review, this changes from:

/data/omnios-build/ksh/linttest: warning: line 12: variable expansion makes arithmetic evaluation less efficient

to

/data/omnios-build/ksh/linttest: warning: line 12: in '(( $a > 1 ))', using '$' is unnecessary, incurs a penalty and can introduce rounding errors.