Create a check that warns about using %p printf specifier

[LegalizeAdulthood]

Bugzilla Link	44108
Version	unspecified
OS	Windows NT

Extended Description

Recently I ran into some surprising behavior surrounding the use of %p in a printf call. On Windows %p with a nullptr prints zeros, but on Linux %p with a nullptr prints "(nil)". This is surprising, but conforming to the standard which states (roughly) that the result of %p is implementation dependent.

Create a check that warns about the potential non-portable output when using %p in a printf or scanf specifier.

[llvmbot]

@llvm/issue-subscribers-good-first-issue

[richmanon]

I have reproduce the issue. Check on windows and linux with the compiler clang and gcc.
The testcase was i written was
#include<stdio.h>
int main()
{
int *pointer=NULL;
printf("%p\n",pointer);
return 0;
}
On windows output was 0000000000000000
On linux output was (nil)

[tensor-ninja]

Myself and @Delta456 @aafeke are taking on this issue

[tensor-ninja]

Submitted patch for review https://reviews.llvm.org/D139604

[llvmbot]

@llvm/issue-subscribers-clang-static-analyzer

[aabhinavg]

On mac i used the command

<main][~/git_repo_for_learning/llvm-project/test]$ ../build/bin/scan-build -enable-checker optin.portability ../build/bin/clang 
-g eg.cpp 
scan-build: Using '/Users//git_repo_for_learning/llvm-project/build/bin/clang-17' for static analysis
scan-build: Analysis run complete.
scan-build: Removing directory '/var/folders/2h/_s0drn1j2j9cd4v00hht7k440000gn/T/scan-build-2023-02-05-205217-54968-1' because it contains no reports.
scan-build: No bugs found.>. 

I got no error

clang version 17.0.0 (https://github.com/llvm/llvm-project 8bb54da)
Target: arm64-apple-darwin21.6.0
Thread model: posix
InstalledDir: /Users/git_repo_for_learning/llvm-project/test/../build/bin

Code for the eg.cpp

#include <stdio.h>
#include <stdlib.h>

int main() {
int *p = nullptr;
printf("%p", p);
}

[tensor-ninja]

Hi @aabhinavg. That is because the my commit was not accepted. I have not had the time to go back and fix the requests needed to land the patch due to school.