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Understanding Memory Management in C: Allocation, Control, and Best Practices

Dive into the world of memory management in C programming with a focus on allocation, control, and the significance of memory resources. Explore critical concepts like malloc, calloc, and realloc functions, alongside practical examples that illustrate their usage. Learn how to check for sufficient memory before allocation, handle dynamic memory, and prevent memory leaks through effective memory management practices. This guide is essential for both beginners and experienced programmers looking to refine their coding skills and deepen their understanding of memory handling.

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Understanding Memory Management in C: Allocation, Control, and Best Practices

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  1. Mäluhaldus Vol2 Risto Heinsar & Ott Madis Ozolit

  2. Usalda, kuid kontrolli! • Mälu on piiratud ressurss • Eelmine kord küsisime mälu, kuid mis juhtub, kui meil seda piisavalt pole? #include <stdio.h> #include <malloc.h> intmain(void){ int*ptr1, *ptr2; ptr1=(int*)malloc(sizeof(int)*100); ptr2=(int*)malloc(sizeof(int)*50000000000000000); printf("ptr1 adr = %p\nptr2 adr = %p", ptr1, ptr2); free(ptr1); free(ptr2); return 0; }

  3. Usalda, kuid kontrolli! • Mälu on piiratud ressurss • Eelmine kord küsisime mälu, kuid mis juhtub, kui meil seda piisavalt pole?

  4. Näide 1 – Mälu allokeerimisekontroll #include <stdio.h> #include <malloc.h> #include <stdlib.h> intmain(void){ int*ptr; ptr=(int*)malloc(sizeof(int)*50000000000000000); if(!ptr) { printf("Pole piisavalt mälu"); exit(0); } return 0; }

  5. calloc(); Calloc() funktsiooni prototüüp:void* calloc (size_tnum, size_t size); • Tagastus tüüpi void* - viit allokeeritud mälule • 1. parameeter num (size_t tüüpi) – mitu elementi • 2.parameeter size (size_t tüüpi) – mitu baiti on üks element • Erinevalt malloc() funktsioonist, initsialiseerib calloc() kogu küsitud mälu nullidega!Realisatsioon:ptr=(int*)calloc(n, sizeof(int));

  6. Näide 2 - calloc intmain(void){ int*ptr,i; ptr=(int*)calloc(5,sizeof(int)); for(i = 0; i < n; i++) printf("%d\n", *(ptr+ i)); return 0; }

  7. realloc(); • Realloc() funktsiooni prototüüp:void* realloc (void* ptr, size_t size); • Tagastus tüüpi void* - viit „uuele“ mälule • 1. parameeter ptr (void* tüüpi) – viit mälule • 2. parameeter size (size_t tüüpi) – uus suurus • Realloc funktsioon lubab meil juba allokeeritud mälu laiendada ja vähendada. Juhul, kui see võimalik pole, tagastatakse NULL. • Realloc töötab ka juhul, kui varemalt pole mälu allokeeritud. • ptr2 =(int*)realloc(ptr, sizeof(int) * n)

  8. Näide 3 – realloc() #include <stdio.h> #include <malloc.h> intmain(void){ int*ptr2=NULL; int*ptr=(int*)malloc(sizeof(int)*100); printf("ptr = %p\n", ptr); ptr2=(int*)realloc(ptr, sizeof(int) * 80000000000); printf("ptr = %p\n", ptr); printf("ptr2 = %p\n", ptr2); free(ptr2); free(ptr); return 0; }

  9. Näide 4 – realloc() #include <stdio.h> #include <malloc.h> intmain (void) { intn, i, *massiiv, *suuremMassiiv; printf("Mitunumbritmassiiv?\n> "); scanf("%d", &n); massiiv= (int*)malloc(sizeof(int) * n); for(i= 0; i< n; i++) scanf("%d", (massiiv+ i)); for(i= 0; i< n; i++) printf(" > %d\n", *(massiiv+ i)); printf("Mitunumbrituusmassiiv?\n> "); scanf("%d", &n); suuremMassiiv= (int*)realloc(massiiv, sizeof(int) * n); for(; i< n; i++) scanf("%d", (suuremMassiiv+ i)); for(i= 0; i< n; i++) printf(" > %d\n", *(suuremMassiiv+ i)); return 0; }

  10. Tunnitöö • Loed failist sisse andmed struktuuriga (malloc) • Char ISBN kood • Char pealkiri • Char autor • Int eksemplaride arv • Lubad kasutajal sisestada täiendavaid kirjeid mällu (realloc) • Enneprogrammi lõppu väljasta uus seis!

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