diff --git a/cmake/compileroptions.cmake b/cmake/compileroptions.cmake
index e9d1f7d4692..968c8bfe239 100644
--- a/cmake/compileroptions.cmake
+++ b/cmake/compileroptions.cmake
@@ -68,6 +68,7 @@ if(CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
     add_compile_options(-Wsuggest-attribute=noreturn)
     add_compile_options(-Wno-shadow)                # whenever a local variable or type declaration shadows another one
     add_compile_options_safe(-Wuseless-cast)
+    # add_compile_options_safe(-Wsuggest-attribute=returns_nonnull) # reports the warning even if the attribute is set
 elseif(CMAKE_CXX_COMPILER_ID MATCHES "Clang")
     if(CMAKE_CXX_COMPILER_VERSION VERSION_EQUAL 14 OR CMAKE_CXX_COMPILER_VERSION VERSION_GREATER 14)
         # TODO: verify this regression still exists in clang-15
diff --git a/lib/clangimport.cpp b/lib/clangimport.cpp
index e511079d022..fb11991777f 100644
--- a/lib/clangimport.cpp
+++ b/lib/clangimport.cpp
@@ -362,7 +362,7 @@ namespace clangimport {
         void addFullScopeNameTokens(TokenList &tokenList, const Scope *recordScope);
         Scope *createScope(TokenList &tokenList, Scope::ScopeType scopeType, AstNodePtr astNode, const Token *def);
         Scope *createScope(TokenList &tokenList, Scope::ScopeType scopeType, const std::vector<AstNodePtr> &children2, const Token *def);
-        Token *createTokensCall(TokenList &tokenList);
+        RET_NONNULL Token *createTokensCall(TokenList &tokenList);
         void createTokensFunctionDecl(TokenList &tokenList);
         void createTokensForCXXRecord(TokenList &tokenList);
         Token *createTokensVarDecl(TokenList &tokenList);
diff --git a/lib/config.h b/lib/config.h
index ebd2ebbbe14..1932364001f 100644
--- a/lib/config.h
+++ b/lib/config.h
@@ -121,11 +121,11 @@
 #  define DEPRECATED
 #endif
 
-// TODO: GCC apparently also supports this but there is no documentation on it
 // returns_nonnull
 #if __has_cpp_attribute (gnu::returns_nonnull)
 #  define RET_NONNULL [[gnu::returns_nonnull]]
-#elif (defined(__clang__) && ((__clang_major__ > 3) || ((__clang_major__ == 3) && (__clang_minor__ >= 7))))
+#elif (defined(__clang__) && ((__clang_major__ > 3) || ((__clang_major__ == 3) && (__clang_minor__ >= 7)))) \
+    || (defined(__GNUC__) && (__GNUC__ >= 9))
 #  define RET_NONNULL __attribute__((returns_nonnull))
 #else
 #  define RET_NONNULL
diff --git a/lib/cppcheck.cpp b/lib/cppcheck.cpp
index 8668db48a3f..435f1b17ecb 100644
--- a/lib/cppcheck.cpp
+++ b/lib/cppcheck.cpp
@@ -1103,8 +1103,8 @@ void CppCheck::checkNormalTokens(const Tokenizer &tokenizer)
 
     if (mSettings.useSingleJob() || !mSettings.buildDir.empty()) {
         // Analyse the tokens..
-
-        if (CTU::FileInfo * const fi1 = CTU::getFileInfo(tokenizer)) {
+        {
+            CTU::FileInfo * const fi1 = CTU::getFileInfo(tokenizer);
             if (!mSettings.buildDir.empty())
                 mAnalyzerInformation.setFileInfo("ctu", fi1->toString());
             if (mSettings.useSingleJob())
diff --git a/lib/cppcheck.h b/lib/cppcheck.h
index d59716d2662..fda7c6027c8 100644
--- a/lib/cppcheck.h
+++ b/lib/cppcheck.h
@@ -116,7 +116,7 @@ class CPPCHECKLIB CppCheck : ErrorLogger {
      * @brief Returns current version number as a string.
      * @return version, e.g. "1.38"
      */
-    static const char * version();
+    RET_NONNULL static const char * version();
 
     /**
      * @brief Returns extra version info as a string.
@@ -124,7 +124,7 @@ class CPPCHECKLIB CppCheck : ErrorLogger {
      * time/date etc.
      * @return extra version info, e.g. "04d42151" (Git commit id).
      */
-    static const char * extraVersion();
+    RET_NONNULL static const char * extraVersion();
 
     /**
      * @brief Call all "getErrorMessages" in all registered Check classes.
diff --git a/lib/ctu.h b/lib/ctu.h
index dacc430bb0c..1efcae59397 100644
--- a/lib/ctu.h
+++ b/lib/ctu.h
@@ -144,7 +144,7 @@ namespace CTU {
     CPPCHECKLIB std::string getFunctionId(const Tokenizer &tokenizer, const Function *function);
 
     /** @brief Parse current TU and extract file info */
-    CPPCHECKLIB FileInfo *getFileInfo(const Tokenizer &tokenizer);
+    CPPCHECKLIB RET_NONNULL FileInfo *getFileInfo(const Tokenizer &tokenizer);
 
     CPPCHECKLIB std::list<FileInfo::UnsafeUsage> getUnsafeUsage(const Tokenizer &tokenizer, const Settings &settings, bool (*isUnsafeUsage)(const Settings &settings, const Token *argtok, MathLib::bigint *value));
 
diff --git a/lib/symboldatabase.h b/lib/symboldatabase.h
index bba22b78b3f..5a8608e7e7c 100644
--- a/lib/symboldatabase.h
+++ b/lib/symboldatabase.h
@@ -1015,7 +1015,7 @@ class CPPCHECKLIB Function {
     void isInlineKeyword(bool state) {
         setFlag(fIsInlineKeyword, state);
     }
-    const Token *setFlags(const Token *tok1, const Scope *scope);
+    RET_NONNULL const Token *setFlags(const Token *tok1, const Scope *scope);
 };
 
 class CPPCHECKLIB Scope {
@@ -1440,7 +1440,7 @@ class CPPCHECKLIB SymbolDatabase {
     void debugSymbolDatabase() const;
 
     void addClassFunction(Scope *&scope, const Token *&tok, const Token *argStart);
-    static Function *addGlobalFunctionDecl(Scope*& scope, const Token* tok, const Token *argStart, const Token* funcStart);
+    RET_NONNULL static Function *addGlobalFunctionDecl(Scope*& scope, const Token* tok, const Token *argStart, const Token* funcStart);
     Function *addGlobalFunction(Scope*& scope, const Token*& tok, const Token *argStart, const Token* funcStart);
     void addNewFunction(Scope *&scope, const Token *&tok);
     bool isFunction(const Token *tok, const Scope* outerScope, const Token *&funcStart, const Token *&argStart, const Token*& declEnd) const;
diff --git a/lib/templatesimplifier.cpp b/lib/templatesimplifier.cpp
index c2067c94a73..4f76648ae92 100644
--- a/lib/templatesimplifier.cpp
+++ b/lib/templatesimplifier.cpp
@@ -1346,7 +1346,7 @@ void TemplateSimplifier::simplifyTemplateAliases()
                     const Token * const fromStart = args[argnr].first;
                     const Token * const fromEnd   = args[argnr].second->previous();
                     Token *temp = TokenList::copyTokens(tok1, fromStart, fromEnd, true);
-                    const bool tempOK(temp && temp != tok1->next());
+                    const bool tempOK(temp != tok1->next());
                     tok1->deleteThis();
                     if (tempOK)
                         tok1 = temp; // skip over inserted parameters
diff --git a/lib/tokenize.cpp b/lib/tokenize.cpp
index d3211f35d74..e16cd83a681 100644
--- a/lib/tokenize.cpp
+++ b/lib/tokenize.cpp
@@ -2152,9 +2152,6 @@ void Tokenizer::simplifyTypedefCpp()
 
                         tok2 = TokenList::copyTokens(tok2, argStart, argEnd);
                         if (inTemplate) {
-                            if (!tok2)
-                                syntaxError(nullptr);
-
                             tok2 = tok2->next();
                         }
 
diff --git a/lib/tokenize.h b/lib/tokenize.h
index 46cf44f7cdc..1793ceb1c07 100644
--- a/lib/tokenize.h
+++ b/lib/tokenize.h
@@ -172,7 +172,7 @@ class CPPCHECKLIB Tokenizer {
      * '; int *p(0);' => '; int *p = 0;'
      */
     void simplifyInitVar();
-    static Token* initVar(Token* tok);
+    RET_NONNULL static Token* initVar(Token* tok);
 
     /**
      * Simplify the location of "static" and "const" qualifiers in
diff --git a/lib/tokenlist.h b/lib/tokenlist.h
index 09a74c4ca16..63e32b673b2 100644
--- a/lib/tokenlist.h
+++ b/lib/tokenlist.h
@@ -94,7 +94,7 @@ class CPPCHECKLIB TokenList {
      * @param one_line true=>copy all tokens to the same line as dest. false=>copy all tokens to dest while keeping the 'line breaks'
      * @return new location of last token copied
      */
-    static Token *copyTokens(Token *dest, const Token *first, const Token *last, bool one_line = true);
+    RET_NONNULL static Token *copyTokens(Token *dest, const Token *first, const Token *last, bool one_line = true);
 
     /**
      * Create tokens from code.
diff --git a/lib/vfvalue.h b/lib/vfvalue.h
index 3eb1dd3b467..0a44a1c230b 100644
--- a/lib/vfvalue.h
+++ b/lib/vfvalue.h
@@ -327,10 +327,10 @@ namespace ValueFlow
 
         enum class LifetimeScope : std::uint8_t { Local, Argument, SubFunction, ThisPointer, ThisValue } lifetimeScope = LifetimeScope::Local;
 
-        static const char* toString(MoveKind moveKind);
-        static const char* toString(LifetimeKind lifetimeKind);
-        static const char* toString(LifetimeScope lifetimeScope);
-        static const char* toString(Bound bound);
+        RET_NONNULL static const char* toString(MoveKind moveKind);
+        RET_NONNULL static const char* toString(LifetimeKind lifetimeKind);
+        RET_NONNULL static const char* toString(LifetimeScope lifetimeScope);
+        RET_NONNULL static const char* toString(Bound bound);
 
         /** How known is this value */
         enum class ValueKind : std::uint8_t {
diff --git a/lib/xml.h b/lib/xml.h
index 86377f77dac..faf121dcdf4 100644
--- a/lib/xml.h
+++ b/lib/xml.h
@@ -22,6 +22,7 @@
 #include "config.h"
 #include "path.h"
 
+SUPPRESS_WARNING_GCC_PUSH("-Wsuggest-attribute=returns_nonnull")
 SUPPRESS_WARNING_CLANG_PUSH("-Wzero-as-null-pointer-constant")
 SUPPRESS_WARNING_CLANG_PUSH("-Wsuggest-destructor-override")
 SUPPRESS_WARNING_CLANG_PUSH("-Winconsistent-missing-destructor-override")
@@ -33,6 +34,7 @@ SUPPRESS_WARNING_CLANG_POP
 SUPPRESS_WARNING_CLANG_POP
 SUPPRESS_WARNING_CLANG_POP
 SUPPRESS_WARNING_CLANG_POP
+SUPPRESS_WARNING_GCC_POP
 
 inline static tinyxml2::XMLError xml_LoadFile(tinyxml2::XMLDocument& doc, const char* filename)
 {