Preprocessor constants not properly handled.

[secure-sw-dev-bot]

This issue was copied from checkedc/checkedc-clang#650

---

[This is a BUG]

Looks like checkedc-clang does not support preprocessor constants:

Consider the following code:

#include<stdio_checked.h>
void log_write(_Ptr<const char> func) {
    char pre[256];
    snprintf(pre, sizeof(pre), "%s", func);
    printf("%s", pre);
}
int main(void) {
   log_write("This Works");
   log_write(__func__);
}

$ clang -c pre.c 
pre.c:9:14: error: expression has unknown bounds, cast to ptr<T> expects source to have bounds
   log_write(__func__);
             ^~~~~~~~
1 error generated.

Note that, log_write("This Works"); checks out.

[secure-sw-dev-bot]

Comment from @mgrang:

Reduced test case:

void foo() {
  _Ptr<const char> func = __func__;
}

[secure-sw-dev-bot]

Comment from @mgrang:

This is fixed in checkedc/checkedc-clang#673.
@Machiry Could you please verify that the above PR fixes this issue?

[secure-sw-dev-bot]

Comment from @Machiry:

It works. Thank you for fixing this.

[secure-sw-dev-bot]

Comment from @mgrang:

Added runtime tests checkedc/checkedc#380.