[-Wunsafe-buffer-usage] Fix a bug and suppress libc warnings for C files (#109496)

- Fix a bug in UnsafeBufferUsage.cpp related to casting to PointerType
- Suppress -Wunsafe-buffer-usage-in-libc-call for C files

(rdar://117182250)

Author: ziqingluo-90

clang/lib/Analysis/UnsafeBufferUsage.cpp

@@ -250,7 +250,9 @@ AST_MATCHER_P(Stmt, ignoreUnsafeBufferInContainer,
 
 AST_MATCHER_P(Stmt, ignoreUnsafeLibcCall, const UnsafeBufferUsageHandler *,
               Handler) {
-  return Handler->ignoreUnsafeBufferInLibcCall(Node.getBeginLoc());
+  if (Finder->getASTContext().getLangOpts().CPlusPlus)
+    return Handler->ignoreUnsafeBufferInLibcCall(Node.getBeginLoc());
+  return true; /* Only warn about libc calls for C++ */
 }
 
 AST_MATCHER_P(CastExpr, castSubExpr, internal::Matcher<Expr>, innerMatcher) {
@@ -784,12 +786,12 @@ AST_MATCHER_P(CallExpr, hasUnsafePrintfStringArg,
     return false; // possibly some user-defined printf function
 
   ASTContext &Ctx = Finder->getASTContext();
-  QualType FristParmTy = FD->getParamDecl(0)->getType();
+  QualType FirstParmTy = FD->getParamDecl(0)->getType();
 
-  if (!FristParmTy->isPointerType())
+  if (!FirstParmTy->isPointerType())
     return false; // possibly some user-defined printf function
 
-  QualType FirstPteTy = (cast<PointerType>(FristParmTy))->getPointeeType();
+  QualType FirstPteTy = FirstParmTy->castAs<PointerType>()->getPointeeType();
 
   if (!Ctx.getFILEType()
            .isNull() && //`FILE *` must be in the context if it is fprintf
@@ -865,7 +867,7 @@ AST_MATCHER(CallExpr, hasUnsafeSnprintfBuffer) {
   if (!FirstParmTy->isPointerType())
     return false; // Not an snprint
 
-  QualType FirstPteTy = cast<PointerType>(FirstParmTy)->getPointeeType();
+  QualType FirstPteTy = FirstParmTy->castAs<PointerType>()->getPointeeType();
   const Expr *Buf = Node.getArg(0), *Size = Node.getArg(1);
 
   if (FirstPteTy.isConstQualified() || !Buf->getType()->isPointerType() ||

clang/lib/Sema/AnalysisBasedWarnings.cpp

@@ -2581,7 +2581,8 @@ void clang::sema::AnalysisBasedWarnings::IssueWarnings(
       !Diags.isIgnored(diag::warn_unsafe_buffer_variable, SourceLocation()) ||
       !Diags.isIgnored(diag::warn_unsafe_buffer_usage_in_container,
                        SourceLocation()) ||
-      !Diags.isIgnored(diag::warn_unsafe_buffer_libc_call, SourceLocation())) {
+      (!Diags.isIgnored(diag::warn_unsafe_buffer_libc_call, SourceLocation()) &&
+       S.getLangOpts().CPlusPlus /* only warn about libc calls in C++ */)) {
     CallableVisitor(CallAnalyzers).TraverseTranslationUnitDecl(TU);
   }
 }

clang/test/SemaCXX/warn-unsafe-buffer-usage-libc-functions.cpp

@@ -1,5 +1,7 @@
 // RUN: %clang_cc1 -std=c++20 -Wno-all -Wunsafe-buffer-usage \
 // RUN:            -verify %s
+// RUN: %clang_cc1 -std=c++20 -Wno-all -Wunsafe-buffer-usage \
+// RUN:            -verify %s -x objective-c++
 // RUN: %clang_cc1 -std=c++20 -Wno-all -Wunsafe-buffer-usage-in-libc-call \
 // RUN:            -verify %s
 
@@ -56,6 +58,11 @@ namespace std {
 }
 
 void f(char * p, char * q, std::span<char> s, std::span<char> s2) {
+  typedef FILE * _Nullable aligned_file_ptr_t __attribute__((align_value(64)));
+  typedef char * _Nullable aligned_char_ptr_t __attribute__((align_value(64)));
+  aligned_file_ptr_t fp;
+  aligned_char_ptr_t cp;
+
   memcpy();                   // expected-warning{{function 'memcpy' is unsafe}}
   std::memcpy();              // expected-warning{{function 'memcpy' is unsafe}}
   __builtin_memcpy(p, q, 64); // expected-warning{{function '__builtin_memcpy' is unsafe}}
@@ -71,9 +78,11 @@ void f(char * p, char * q, std::span<char> s, std::span<char> s2) {
   printf("%s%d", // expected-warning{{function 'printf' is unsafe}}
 	 p,    // expected-note{{string argument is not guaranteed to be null-terminated}} note attached to the unsafe argument
 	 *p);
+  printf(cp, p, *p); // expected-warning{{function 'printf' is unsafe}} // expected-note{{string argument is not guaranteed to be null-terminated}}
   sprintf(q, "%s%d", "hello", *p); // expected-warning{{function 'sprintf' is unsafe}} expected-note{{change to 'snprintf' for explicit bounds checking}}
   swprintf(q, "%s%d", "hello", *p); // expected-warning{{function 'swprintf' is unsafe}} expected-note{{change to 'snprintf' for explicit bounds checking}}
   snprintf(q, 10, "%s%d", "hello", *p); // expected-warning{{function 'snprintf' is unsafe}} expected-note{{buffer pointer and size may not match}}
+  snprintf(cp, 10, "%s%d", "hello", *p); // expected-warning{{function 'snprintf' is unsafe}} expected-note{{buffer pointer and size may not match}}
   snprintf(s.data(), s2.size(), "%s%d", "hello", *p); // expected-warning{{function 'snprintf' is unsafe}} expected-note{{buffer pointer and size may not match}}
   snwprintf(s.data(), s2.size(), "%s%d", "hello", *p); // expected-warning{{function 'snwprintf' is unsafe}} expected-note{{buffer pointer and size may not match}}
   snwprintf_s(                      // expected-warning{{function 'snwprintf_s' is unsafe}}
@@ -84,15 +93,18 @@ void f(char * p, char * q, std::span<char> s, std::span<char> s2) {
   sscanf(p, "%s%d", "hello", *p);    // expected-warning{{function 'sscanf' is unsafe}}
   sscanf_s(p, "%s%d", "hello", *p);  // expected-warning{{function 'sscanf_s' is unsafe}}
   fprintf((FILE*)p, "%P%d%p%i hello world %32s", *p, *p, p, *p, p); // expected-warning{{function 'fprintf' is unsafe}} expected-note{{string argument is not guaranteed to be null-terminated}}
+  fprintf(fp, "%P%d%p%i hello world %32s", *p, *p, p, *p, p); // expected-warning{{function 'fprintf' is unsafe}} expected-note{{string argument is not guaranteed to be null-terminated}}
   wprintf(L"hello %s", p); // expected-warning{{function 'wprintf' is unsafe}} expected-note{{string argument is not guaranteed to be null-terminated}}
 
+
   char a[10], b[11];
   int c[10];
   std::wstring WS;
 
   snprintf(a, sizeof(b), "%s", __PRETTY_FUNCTION__);         // expected-warning{{function 'snprintf' is unsafe}} expected-note{{buffer pointer and size may not match}}
   snprintf((char*)c, sizeof(c), "%s", __PRETTY_FUNCTION__);  // expected-warning{{function 'snprintf' is unsafe}} expected-note{{buffer pointer and size may not match}}
   fprintf((FILE*)p, "%P%d%p%i hello world %32s", *p, *p, p, *p, "hello"); // no warn
+  fprintf(fp, "%P%d%p%i hello world %32s", *p, *p, p, *p, "hello"); // no warn
   printf("%s%d", "hello", *p); // no warn
   snprintf(s.data(), s.size_bytes(), "%s%d", "hello", *p); // no warn
   snprintf(s.data(), s.size_bytes(), "%s%d", __PRETTY_FUNCTION__, *p); // no warn

clang/test/SemaCXX/warn-unsafe-buffer-usage-no-libc-functions-in-c.c

@@ -0,0 +1,10 @@
+// RUN: %clang_cc1 -Wunsafe-buffer-usage %s -verify %s -x c
+// RUN: %clang_cc1 -Wunsafe-buffer-usage %s -verify %s -x objective-c
+
+void* __asan_memcpy(void *dst,const void *src, unsigned long size);
+
+void f(int *p, int *q) {
+
+  __asan_memcpy(p, q, 10); // no libc warn in C
+  ++p[5];           // expected-warning{{unsafe buffer access}}
+}