1 files changed, 11 insertions, 8 deletions
diff --git a/absl/strings/str_cat.cc b/absl/strings/str_cat.cc
index 900dc69a..e7f7052a 100644
--- a/absl/strings/str_cat.cc
+++ b/absl/strings/str_cat.cc
@@ -23,6 +23,7 @@
 #include <string>
 
 #include "absl/base/config.h"
+#include "absl/base/nullability.h"
 #include "absl/strings/internal/resize_uninitialized.h"
 #include "absl/strings/string_view.h"
 
@@ -40,7 +41,8 @@ ABSL_NAMESPACE_BEGIN
 namespace {
 // Append is merely a version of memcpy that returns the address of the byte
 // after the area just overwritten.
-inline char* Append(char* out, const AlphaNum& x) {
+inline absl::Nonnull<char*> Append(absl::Nonnull<char*> out,
+                                   const AlphaNum& x) {
   // memcpy is allowed to overwrite arbitrary memory, so doing this after the
   // call would force an extra fetch of x.size().
   char* after = out + x.size();
@@ -128,7 +130,7 @@ std::string CatPieces(std::initializer_list<absl::string_view> pieces) {
   assert(((src).size() == 0) ||      \
          (uintptr_t((src).data() - (dest).data()) > uintptr_t((dest).size())))
 
-void AppendPieces(std::string* dest,
+void AppendPieces(absl::Nonnull<std::string*> dest,
                   std::initializer_list<absl::string_view> pieces) {
   size_t old_size = dest->size();
   size_t to_append = 0;
@@ -152,7 +154,7 @@ void AppendPieces(std::string* dest,
 
 }  // namespace strings_internal
 
-void StrAppend(std::string* dest, const AlphaNum& a) {
+void StrAppend(absl::Nonnull<std::string*> dest, const AlphaNum& a) {
   ASSERT_NO_OVERLAP(*dest, a);
   std::string::size_type old_size = dest->size();
   STLStringAppendUninitializedAmortized(dest, a.size());
@@ -162,7 +164,8 @@ void StrAppend(std::string* dest, const AlphaNum& a) {
   assert(out == begin + dest->size());
 }
 
-void StrAppend(std::string* dest, const AlphaNum& a, const AlphaNum& b) {
+void StrAppend(absl::Nonnull<std::string*> dest, const AlphaNum& a,
+               const AlphaNum& b) {
   ASSERT_NO_OVERLAP(*dest, a);
   ASSERT_NO_OVERLAP(*dest, b);
   std::string::size_type old_size = dest->size();
@@ -174,8 +177,8 @@ void StrAppend(std::string* dest, const AlphaNum& a, const AlphaNum& b) {
   assert(out == begin + dest->size());
 }
 
-void StrAppend(std::string* dest, const AlphaNum& a, const AlphaNum& b,
-               const AlphaNum& c) {
+void StrAppend(absl::Nonnull<std::string*> dest, const AlphaNum& a,
+               const AlphaNum& b, const AlphaNum& c) {
   ASSERT_NO_OVERLAP(*dest, a);
   ASSERT_NO_OVERLAP(*dest, b);
   ASSERT_NO_OVERLAP(*dest, c);
@@ -189,8 +192,8 @@ void StrAppend(std::string* dest, const AlphaNum& a, const AlphaNum& b,
   assert(out == begin + dest->size());
 }
 
-void StrAppend(std::string* dest, const AlphaNum& a, const AlphaNum& b,
-               const AlphaNum& c, const AlphaNum& d) {
+void StrAppend(absl::Nonnull<std::string*> dest, const AlphaNum& a,
+               const AlphaNum& b, const AlphaNum& c, const AlphaNum& d) {
   ASSERT_NO_OVERLAP(*dest, a);
   ASSERT_NO_OVERLAP(*dest, b);
   ASSERT_NO_OVERLAP(*dest, c);