am stuck with something simple which is concating string not sure what am doing wrong , am getting exception (3 ) error due to it

3   LoadStoreErrorCause Processor internal physical address or data error during load or store

my code

    String HOST = "useotools.com";
    String API_URL = "/iot/api.php";   // API URL
    uint16_t HTTPS_PORT = 4000;  // HTTPS port
    uint16_t HTTP_PORT = 4001;  // HTTP port

void https_request_function(){
String HOST_URL = "http://"+String(HOST)+":"+String(HTTP_PORT)+String(API_URL)+"";


when first time https_request_function() is called then HOST_URL is displayed correctly and on 2nd time when this function is called by code it trigger exception(3) which is strange .

  • see CStringBuilderExample in my StreamLib (it is in Library Manager) – Juraj Oct 3 '19 at 13:09
  • 1
    related: stackoverflow.com/q/308695/3984613 (as this is not entirely specific to Arduino) – Ghanima Oct 3 '19 at 13:32
  • @Ghanima thanks i tired like this but still on 2nd call it print weird boxes snprintf(HOST_URL, sizeof HOST_URL, "%s%s%s%d%s", "http://",HOST.c_str(),":",HTTP_PORT,API_URL.c_str()); – user889030 Oct 3 '19 at 14:01
  • @Juraj that string builder lib not exists in esp boards :( – user889030 Oct 3 '19 at 14:02
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