Clang has traditionally allowed C programs to implicitly convert
integers to pointers and pointers to integers, despite it not being
valid to do so except under special circumstances (like converting the
integer 0, which is the null pointer constant, to a pointer). In C89,
this would result in undefined behavior per 3.3.4, and in C99 this rule
was strengthened to be a constraint violation instead. Constraint
violations are most often handled as an error.
This patch changes the warning to default to an error in all C modes
(it is already an error in C++). This gives us better security posture
by calling out potential programmer mistakes in code but still allows
users who need this behavior to use -Wno-error=int-conversion to retain
the warning behavior, or -Wno-int-conversion to silence the diagnostic
entirely.
Differential Revision: https://reviews.llvm.org/D129881
Compared to the old implementation:
* In C++, we only recurse into aggregate classes.
* Unnamed bit-fields are not printed.
* Constant evaluation is supported.
* Proper conversion is done when passing arguments through `...`.
* Additional arguments are supported and are injected prior to the
format string; this directly supports use with `fprintf`, for example.
* An arbitrary callable can be passed rather than only a function
pointer. In particular, in C++, a function template or overload set is
acceptable.
* All text generated by Clang is printed via `%s` rather than directly;
this avoids issues where Clang's pretty-printing output might itself
contain a `%` character.
* Fields of types that we don't know how to print are printed with a
`"*%p"` format and passed by address to the print function.
* No return value is produced.
Reviewed By: aaron.ballman, erichkeane, yihanaa
Differential Revision: https://reviews.llvm.org/D124221
This patch adds -Wno-strict-prototypes to all of the test cases that
use functions without prototypes, but not as the primary concern of the
test. e.g., attributes testing whether they can/cannot be applied to a
function without a prototype, etc.
This is done in preparation for enabling -Wstrict-prototypes by
default.
Aaron Ballman