function returns address of local variable in c [duplicate]

Answer 1

You SHOULD NOT (although yes, sometimes it CAN return the expected result!) return local variable pointer from a function as it is allocated on stack!

Here's an excellent explanation as to why: Can a local variable's memory be accessed outside its scope?

To make your code work,replace

char cadena_nueva[largo_texto+1]; 

with

char* cadena_nueva = (char*)malloc(sizeof(char)*(largo_texto+1));

Don't forget to free() it when you are done using it

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It would really help you if you'd read about heap & stack memory storage:

What and where are the stack and heap? http://gribblelab.org/CBootcamp/7_Memory_Stack_vs_Heap.html http://www-ee.eng.hawaii.edu/~tep/EE160/Book/chap14/subsection2.1.1.8.html