c - Extra characters added to beginning of string? -

-

i have 2 characters being added beginning of string , can't seem find out why. characters don't appear in code. i'm @ loss here. code:

#include <stdlib.h> #include <stdio.h> #include <string.h>  char *chars;  char* vector(char input, char *newlist);  int main(){      char *input, *out = "input: ";      printf("enter characters: ");                        while(1){         char = getchar();                         //get input         if(i == '\n'){             break;                                  //detect return key         } else{             input = vector(i, input);               //call vector         }     }      char * print = (char *)malloc(1 + strlen(input) + strlen(out));     strcpy(print, out);                             //concat strings     strcat(print, input);      printf("\n%s", print);                          //print array      free(print);     free(input);     free(chars);      return 0;                                       //exit }  char* vector(char in, char *newlist){      int length = strlen(newlist);                   //determine length of newlist(input)      chars = (char*)calloc(length+2, sizeof(char));  //allocate more memory     strcpy(chars, newlist);                         //copy array chars     chars[length] = in;                             //appened new character     chars[length + 1] = '\0';                       //append end character      return chars; }

for reason, code produces this:

enter characters: gggg  input: pegggg

when should producing this:

enter characters: gggg  input: gggg

you passed uninitialized input vector() , used it, invoked undefined behavior.

try changing char *input char *input = "".

also remove free(chars);, or encounter double-free problem.


Comments

Post a Comment

Popular posts from this blog

c# - How Configure Devart dotConnect for SQLite Code First? -

-
can configure following sample code ? when run following code, error : no entity framework provider found ado.net provider invariant name 'devart.data.sqlite' setting in machine.config <system.data> <dbproviderfactories> <add name="dotconnect sqlite" invariant="devart.data.sqlite" description="devart dotconnect sqlite" type="devart.data.sqlite.sqliteproviderfactory, devart.data.sqlite, version=4.6.287.0, culture=neutral, publickeytoken=09af7300eec23701" /> </dbproviderfactories> </system.data> after add below block code in app.config <?xml version="1.0"?> <configuration>   <configsections> <!-- more information on entity framework configuration, visit http://go.microsoft.com/fwlink/?linkid=237468 --> <section name="entityframework" type="system.data.entity.internal.configfile.entityframeworksection, entit...
Read more

java - Copying object fields -

-
what best way of copying classes when need have 2 independent variables? have simple class: public class myclass { boolean = false; string b= "not empty"; } do need make method : assign(myclass data ) { a= data.a; b= data.b; } is there automatic method copy (duplicate) objects in java? do need make method : pretty close. instead of making method, should make constructor. such constructors called copy constructor , , create them this: myclass(myclass data) { = data.a; b = data.b; } and create copy of instance, use constructor this: myclass obj1 = new myclass(); myclass obj2 = new myclass(obj1); copy constructor can tedious : using copy constructor create deep-copy can tedious, when class has mutable fields. in case, assignment create copy of reference, , not object itself. have create copy of fields (if want deep copy). can go recursive. a better way create deep copy serialize , deserialize object. why not use clone()? ...
Read more

c++ - Clear the memory after returning a vector in a function -

-
i have function processes , stores lot of data in , returns results vector of class. amount of data stored in function tremendous , want clear storage memory of function after finished job. necessary (does function automatically clear memory) or should clear memory function? update: vector<customers> process(char* const *filename, vector<int> id) { vector<customers> list_of_customers; (perform actions) return list_of_customers; } variables defined locally within function automatically released @ end of function scope. destructors objects called, should free memory allocated objects (if objects coded correctly). example of such object std::vector . anything you've allocated new must have corresponding delete release storage. try avoid doing own allocation , use raii instead, i.e. containers or smart pointers.
Read more