[clang-tidy] Fix crash in C language in readability-non-const-parameter (#100461)

Summary:
Fix crash that happen when redeclaration got
different number of parameters than definition.

Fixes #100340

Test Plan: 

Reviewers: 

Subscribers: 

Tasks: 

Tags: 


Differential Revision: https://phabricator.intern.facebook.com/D60250525

Author: PiotrZSL

clang-tools-extra/clang-tidy/readability/NonConstParameterCheck.cpp

@@ -157,9 +157,12 @@ void NonConstParameterCheck::diagnoseNonConstParameters() {
     if (!Function)
       continue;
     unsigned Index = Par->getFunctionScopeIndex();
-    for (FunctionDecl *FnDecl : Function->redecls())
+    for (FunctionDecl *FnDecl : Function->redecls()) {
+      if (FnDecl->getNumParams() <= Index)
+        continue;
       Fixes.push_back(FixItHint::CreateInsertion(
           FnDecl->getParamDecl(Index)->getBeginLoc(), "const "));
+    }
 
     diag(Par->getLocation(), "pointer parameter '%0' can be pointer to const")
         << Par->getName() << Fixes;

clang-tools-extra/test/clang-tidy/checkers/readability/non-const-parameter.c

@@ -0,0 +1,11 @@
+// RUN: %check_clang_tidy %s readability-non-const-parameter %t
+
+static int f();
+
+int f(p)
+  int *p;
+// CHECK-MESSAGES: :[[@LINE-1]]:8: warning: pointer parameter 'p' can be pointer to const [readability-non-const-parameter]
+// CHECK-FIXES: {{^}}  const int *p;{{$}}
+{
+    return *p;
+}