diff --git a/modules/openapi-generator/src/main/resources/C-libcurl/CMakeLists.txt.mustache b/modules/openapi-generator/src/main/resources/C-libcurl/CMakeLists.txt.mustache
index ae635d276b75..dfbd9ee55986 100644
--- a/modules/openapi-generator/src/main/resources/C-libcurl/CMakeLists.txt.mustache
+++ b/modules/openapi-generator/src/main/resources/C-libcurl/CMakeLists.txt.mustache
@@ -6,6 +6,7 @@ cmake_policy(SET CMP0063 NEW)
 set(CMAKE_C_VISIBILITY_PRESET default)
 set(CMAKE_VISIBILITY_INLINES_HIDDEN OFF)
 set(CMAKE_WINDOWS_EXPORT_ALL_SYMBOLS ON)
+set(CMAKE_C_FLAGS "-Werror=implicit-function-declaration -Werror=missing-declarations")
 
 option(BUILD_SHARED_LIBS "Build using shared libraries" ON)
 
@@ -14,7 +15,7 @@ find_package(OpenSSL)
 if (OPENSSL_FOUND)
     message (STATUS "OPENSSL found")
 
-    set(CMAKE_C_FLAGS "-DOPENSSL")
+    set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -DOPENSSL")
     if(CMAKE_VERSION VERSION_LESS 3.4)
         include_directories(${OPENSSL_INCLUDE_DIR})
         include_directories(${OPENSSL_INCLUDE_DIRS})
diff --git a/modules/openapi-generator/src/main/resources/C-libcurl/apiClient.c.mustache b/modules/openapi-generator/src/main/resources/C-libcurl/apiClient.c.mustache
index 899cb22ef7aa..d032b5de1fa8 100644
--- a/modules/openapi-generator/src/main/resources/C-libcurl/apiClient.c.mustache
+++ b/modules/openapi-generator/src/main/resources/C-libcurl/apiClient.c.mustache
@@ -173,7 +173,7 @@ void sslConfig_free(sslConfig_t *sslConfig) {
     free(sslConfig);
 }
 
-void replaceSpaceWithPlus(char *stringToProcess) {
+static void replaceSpaceWithPlus(char *stringToProcess) {
     for(int i = 0; i < strlen(stringToProcess); i++) {
         if(stringToProcess[i] == ' ') {
             stringToProcess[i] = '+';
@@ -181,9 +181,9 @@ void replaceSpaceWithPlus(char *stringToProcess) {
     }
 }
 
-char *assembleTargetUrl(const char  *basePath,
-                        const char  *operationParameter,
-                        list_t    *queryParameters) {
+static char *assembleTargetUrl(const char  *basePath,
+                               const char  *operationParameter,
+                               list_t    *queryParameters) {
     int neededBufferSizeForQueryParameters = 0;
     listEntry_t *listEntry;
 
@@ -234,7 +234,7 @@ char *assembleTargetUrl(const char  *basePath,
     return targetUrl;
 }
 
-char *assembleHeaderField(char *key, char *value) {
+static char *assembleHeaderField(char *key, char *value) {
     char *header = malloc(strlen(key) + strlen(value) + 3);
 
     strcpy(header, key),
@@ -244,13 +244,13 @@ char *assembleHeaderField(char *key, char *value) {
     return header;
 }
 
-void postData(CURL *handle, const char *bodyParameters, size_t bodyParametersLength) {
+static void postData(CURL *handle, const char *bodyParameters, size_t bodyParametersLength) {
     curl_easy_setopt(handle, CURLOPT_POSTFIELDS, bodyParameters);
     curl_easy_setopt(handle, CURLOPT_POSTFIELDSIZE_LARGE,
                      (curl_off_t)bodyParametersLength);
 }
 
-int lengthOfKeyPair(keyValuePair_t *keyPair) {
+static int lengthOfKeyPair(keyValuePair_t *keyPair) {
     long length = 0;
     if((keyPair->key != NULL) &&
        (keyPair->value != NULL) )
diff --git a/modules/openapi-generator/src/main/resources/C-libcurl/model-body.mustache b/modules/openapi-generator/src/main/resources/C-libcurl/model-body.mustache
index ebf15d178911..a835a9b37080 100644
--- a/modules/openapi-generator/src/main/resources/C-libcurl/model-body.mustache
+++ b/modules/openapi-generator/src/main/resources/C-libcurl/model-body.mustache
@@ -376,7 +376,7 @@ cJSON *{{classname}}_convertToJSON({{classname}}_t *{{classname}}) {
     {{/isBoolean}}
     {{#isEnum}}
     {{#isString}}
-    if(cJSON_AddStringToObject(item, "{{{baseName}}}", {{{name}}}{{classname}}_ToString({{{classname}}}->{{{name}}})) == NULL)
+    if(cJSON_AddStringToObject(item, "{{{baseName}}}", {{classname}}_{{name}}_ToString({{{classname}}}->{{{name}}})) == NULL)
     {
     goto fail; //Enum
     }
diff --git a/samples/client/others/c/bearerAuth/CMakeLists.txt b/samples/client/others/c/bearerAuth/CMakeLists.txt
index 2bfcf58899c0..2dc8b7b11ace 100644
--- a/samples/client/others/c/bearerAuth/CMakeLists.txt
+++ b/samples/client/others/c/bearerAuth/CMakeLists.txt
@@ -6,6 +6,7 @@ cmake_policy(SET CMP0063 NEW)
 set(CMAKE_C_VISIBILITY_PRESET default)
 set(CMAKE_VISIBILITY_INLINES_HIDDEN OFF)
 set(CMAKE_WINDOWS_EXPORT_ALL_SYMBOLS ON)
+set(CMAKE_C_FLAGS "-Werror=implicit-function-declaration -Werror=missing-declarations")
 
 option(BUILD_SHARED_LIBS "Build using shared libraries" ON)
 
@@ -14,7 +15,7 @@ find_package(OpenSSL)
 if (OPENSSL_FOUND)
     message (STATUS "OPENSSL found")
 
-    set(CMAKE_C_FLAGS "-DOPENSSL")
+    set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -DOPENSSL")
     if(CMAKE_VERSION VERSION_LESS 3.4)
         include_directories(${OPENSSL_INCLUDE_DIR})
         include_directories(${OPENSSL_INCLUDE_DIRS})
diff --git a/samples/client/others/c/bearerAuth/src/apiClient.c b/samples/client/others/c/bearerAuth/src/apiClient.c
index 6614016d27ae..b9f52e2e1b7f 100644
--- a/samples/client/others/c/bearerAuth/src/apiClient.c
+++ b/samples/client/others/c/bearerAuth/src/apiClient.c
@@ -89,7 +89,7 @@ void sslConfig_free(sslConfig_t *sslConfig) {
     free(sslConfig);
 }
 
-void replaceSpaceWithPlus(char *stringToProcess) {
+static void replaceSpaceWithPlus(char *stringToProcess) {
     for(int i = 0; i < strlen(stringToProcess); i++) {
         if(stringToProcess[i] == ' ') {
             stringToProcess[i] = '+';
@@ -97,9 +97,9 @@ void replaceSpaceWithPlus(char *stringToProcess) {
     }
 }
 
-char *assembleTargetUrl(const char  *basePath,
-                        const char  *operationParameter,
-                        list_t    *queryParameters) {
+static char *assembleTargetUrl(const char  *basePath,
+                               const char  *operationParameter,
+                               list_t    *queryParameters) {
     int neededBufferSizeForQueryParameters = 0;
     listEntry_t *listEntry;
 
@@ -150,7 +150,7 @@ char *assembleTargetUrl(const char  *basePath,
     return targetUrl;
 }
 
-char *assembleHeaderField(char *key, char *value) {
+static char *assembleHeaderField(char *key, char *value) {
     char *header = malloc(strlen(key) + strlen(value) + 3);
 
     strcpy(header, key),
@@ -160,13 +160,13 @@ char *assembleHeaderField(char *key, char *value) {
     return header;
 }
 
-void postData(CURL *handle, const char *bodyParameters, size_t bodyParametersLength) {
+static void postData(CURL *handle, const char *bodyParameters, size_t bodyParametersLength) {
     curl_easy_setopt(handle, CURLOPT_POSTFIELDS, bodyParameters);
     curl_easy_setopt(handle, CURLOPT_POSTFIELDSIZE_LARGE,
                      (curl_off_t)bodyParametersLength);
 }
 
-int lengthOfKeyPair(keyValuePair_t *keyPair) {
+static int lengthOfKeyPair(keyValuePair_t *keyPair) {
     long length = 0;
     if((keyPair->key != NULL) &&
        (keyPair->value != NULL) )
diff --git a/samples/client/petstore/c-useJsonUnformatted/CMakeLists.txt b/samples/client/petstore/c-useJsonUnformatted/CMakeLists.txt
index c97fd637cdb9..c5a0b31ca181 100644
--- a/samples/client/petstore/c-useJsonUnformatted/CMakeLists.txt
+++ b/samples/client/petstore/c-useJsonUnformatted/CMakeLists.txt
@@ -6,6 +6,7 @@ cmake_policy(SET CMP0063 NEW)
 set(CMAKE_C_VISIBILITY_PRESET default)
 set(CMAKE_VISIBILITY_INLINES_HIDDEN OFF)
 set(CMAKE_WINDOWS_EXPORT_ALL_SYMBOLS ON)
+set(CMAKE_C_FLAGS "-Werror=implicit-function-declaration -Werror=missing-declarations")
 
 option(BUILD_SHARED_LIBS "Build using shared libraries" ON)
 
@@ -14,7 +15,7 @@ find_package(OpenSSL)
 if (OPENSSL_FOUND)
     message (STATUS "OPENSSL found")
 
-    set(CMAKE_C_FLAGS "-DOPENSSL")
+    set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -DOPENSSL")
     if(CMAKE_VERSION VERSION_LESS 3.4)
         include_directories(${OPENSSL_INCLUDE_DIR})
         include_directories(${OPENSSL_INCLUDE_DIRS})
diff --git a/samples/client/petstore/c-useJsonUnformatted/model/order.c b/samples/client/petstore/c-useJsonUnformatted/model/order.c
index bbbc50e1a316..055dd08a3896 100644
--- a/samples/client/petstore/c-useJsonUnformatted/model/order.c
+++ b/samples/client/petstore/c-useJsonUnformatted/model/order.c
@@ -94,7 +94,7 @@ cJSON *order_convertToJSON(order_t *order) {
 
     // order->status
     if(order->status != openapi_petstore_order_STATUS_NULL) {
-    if(cJSON_AddStringToObject(item, "status", statusorder_ToString(order->status)) == NULL)
+    if(cJSON_AddStringToObject(item, "status", order_status_ToString(order->status)) == NULL)
     {
     goto fail; //Enum
     }
diff --git a/samples/client/petstore/c-useJsonUnformatted/model/pet.c b/samples/client/petstore/c-useJsonUnformatted/model/pet.c
index d95d672eda00..2472e769095d 100644
--- a/samples/client/petstore/c-useJsonUnformatted/model/pet.c
+++ b/samples/client/petstore/c-useJsonUnformatted/model/pet.c
@@ -148,7 +148,7 @@ cJSON *pet_convertToJSON(pet_t *pet) {
 
     // pet->status
     if(pet->status != openapi_petstore_pet_STATUS_NULL) {
-    if(cJSON_AddStringToObject(item, "status", statuspet_ToString(pet->status)) == NULL)
+    if(cJSON_AddStringToObject(item, "status", pet_status_ToString(pet->status)) == NULL)
     {
     goto fail; //Enum
     }
diff --git a/samples/client/petstore/c-useJsonUnformatted/src/apiClient.c b/samples/client/petstore/c-useJsonUnformatted/src/apiClient.c
index 302cb8bff342..ad06a341a4bb 100644
--- a/samples/client/petstore/c-useJsonUnformatted/src/apiClient.c
+++ b/samples/client/petstore/c-useJsonUnformatted/src/apiClient.c
@@ -116,7 +116,7 @@ void sslConfig_free(sslConfig_t *sslConfig) {
     free(sslConfig);
 }
 
-void replaceSpaceWithPlus(char *stringToProcess) {
+static void replaceSpaceWithPlus(char *stringToProcess) {
     for(int i = 0; i < strlen(stringToProcess); i++) {
         if(stringToProcess[i] == ' ') {
             stringToProcess[i] = '+';
@@ -124,9 +124,9 @@ void replaceSpaceWithPlus(char *stringToProcess) {
     }
 }
 
-char *assembleTargetUrl(const char  *basePath,
-                        const char  *operationParameter,
-                        list_t    *queryParameters) {
+static char *assembleTargetUrl(const char  *basePath,
+                               const char  *operationParameter,
+                               list_t    *queryParameters) {
     int neededBufferSizeForQueryParameters = 0;
     listEntry_t *listEntry;
 
@@ -177,7 +177,7 @@ char *assembleTargetUrl(const char  *basePath,
     return targetUrl;
 }
 
-char *assembleHeaderField(char *key, char *value) {
+static char *assembleHeaderField(char *key, char *value) {
     char *header = malloc(strlen(key) + strlen(value) + 3);
 
     strcpy(header, key),
@@ -187,13 +187,13 @@ char *assembleHeaderField(char *key, char *value) {
     return header;
 }
 
-void postData(CURL *handle, const char *bodyParameters, size_t bodyParametersLength) {
+static void postData(CURL *handle, const char *bodyParameters, size_t bodyParametersLength) {
     curl_easy_setopt(handle, CURLOPT_POSTFIELDS, bodyParameters);
     curl_easy_setopt(handle, CURLOPT_POSTFIELDSIZE_LARGE,
                      (curl_off_t)bodyParametersLength);
 }
 
-int lengthOfKeyPair(keyValuePair_t *keyPair) {
+static int lengthOfKeyPair(keyValuePair_t *keyPair) {
     long length = 0;
     if((keyPair->key != NULL) &&
        (keyPair->value != NULL) )
diff --git a/samples/client/petstore/c/model/order.c b/samples/client/petstore/c/model/order.c
index bbbc50e1a316..055dd08a3896 100644
--- a/samples/client/petstore/c/model/order.c
+++ b/samples/client/petstore/c/model/order.c
@@ -94,7 +94,7 @@ cJSON *order_convertToJSON(order_t *order) {
 
     // order->status
     if(order->status != openapi_petstore_order_STATUS_NULL) {
-    if(cJSON_AddStringToObject(item, "status", statusorder_ToString(order->status)) == NULL)
+    if(cJSON_AddStringToObject(item, "status", order_status_ToString(order->status)) == NULL)
     {
     goto fail; //Enum
     }
diff --git a/samples/client/petstore/c/model/pet.c b/samples/client/petstore/c/model/pet.c
index d95d672eda00..2472e769095d 100644
--- a/samples/client/petstore/c/model/pet.c
+++ b/samples/client/petstore/c/model/pet.c
@@ -148,7 +148,7 @@ cJSON *pet_convertToJSON(pet_t *pet) {
 
     // pet->status
     if(pet->status != openapi_petstore_pet_STATUS_NULL) {
-    if(cJSON_AddStringToObject(item, "status", statuspet_ToString(pet->status)) == NULL)
+    if(cJSON_AddStringToObject(item, "status", pet_status_ToString(pet->status)) == NULL)
     {
     goto fail; //Enum
     }
diff --git a/samples/client/petstore/c/src/apiClient.c b/samples/client/petstore/c/src/apiClient.c
index 302cb8bff342..ad06a341a4bb 100644
--- a/samples/client/petstore/c/src/apiClient.c
+++ b/samples/client/petstore/c/src/apiClient.c
@@ -116,7 +116,7 @@ void sslConfig_free(sslConfig_t *sslConfig) {
     free(sslConfig);
 }
 
-void replaceSpaceWithPlus(char *stringToProcess) {
+static void replaceSpaceWithPlus(char *stringToProcess) {
     for(int i = 0; i < strlen(stringToProcess); i++) {
         if(stringToProcess[i] == ' ') {
             stringToProcess[i] = '+';
@@ -124,9 +124,9 @@ void replaceSpaceWithPlus(char *stringToProcess) {
     }
 }
 
-char *assembleTargetUrl(const char  *basePath,
-                        const char  *operationParameter,
-                        list_t    *queryParameters) {
+static char *assembleTargetUrl(const char  *basePath,
+                               const char  *operationParameter,
+                               list_t    *queryParameters) {
     int neededBufferSizeForQueryParameters = 0;
     listEntry_t *listEntry;
 
@@ -177,7 +177,7 @@ char *assembleTargetUrl(const char  *basePath,
     return targetUrl;
 }
 
-char *assembleHeaderField(char *key, char *value) {
+static char *assembleHeaderField(char *key, char *value) {
     char *header = malloc(strlen(key) + strlen(value) + 3);
 
     strcpy(header, key),
@@ -187,13 +187,13 @@ char *assembleHeaderField(char *key, char *value) {
     return header;
 }
 
-void postData(CURL *handle, const char *bodyParameters, size_t bodyParametersLength) {
+static void postData(CURL *handle, const char *bodyParameters, size_t bodyParametersLength) {
     curl_easy_setopt(handle, CURLOPT_POSTFIELDS, bodyParameters);
     curl_easy_setopt(handle, CURLOPT_POSTFIELDSIZE_LARGE,
                      (curl_off_t)bodyParametersLength);
 }
 
-int lengthOfKeyPair(keyValuePair_t *keyPair) {
+static int lengthOfKeyPair(keyValuePair_t *keyPair) {
     long length = 0;
     if((keyPair->key != NULL) &&
        (keyPair->value != NULL) )