Checked-c-convert: Static modifier removed from function declaration when return value converted

[AnnaKornfeldSimpson]

Static modifiers preceding the return type of a function are removed from the declaration when the return type is converted from * to _Ptr.

Example: parson.checked.c:94
Original code: parson.c:94
I have not yet seen a specific error message for this yet; I just noticed while comparing sources.

To use this test case:

• Clone https://github.com/AnnaKornfeldSimpson/parson
• Check out the snapshotWeUse branch
• make test to build the original code. make testchecked to build with the copies produced by checked-c-convert.
• convert.sh runs checked-c-convert on the original code and outputs to *checked* files. If you re-run it, also edit parson.checked.c to use parson.checked.h. convert.sh may need modifications to run in Windows.
• Compiler errors can be compared with compilerErrors.txt (produced on a Ubuntu system, not sure if it will perfectly match in Windows)

[AnnaKornfeldSimpson]

I'm not sure I know precisely all the implications of static on a function in c.
@dtarditi Is this a correctness issue or more stylistic?

[dtarditi]

@AnnaKornfeldSimpson, it could cause name collisions. A static function is local to the C file being compiled. If the static modifier is dropped, the function becomes globally scoped. This could cause a name collision if two separate files defined the same static function.

[dtarditi]

The convert tool has been mostly rewritten (see PR #642). Please reopen this issue if it still exists.