Debugging exercises

Spoofer · Broadcaster Posts: 14 Join date: 2008-04-29

Enas kalos programmatisths einai must na xerei na vriskei kai na diorthwnei ta lathh tou grhgora kai eukola, fusika oxi mono ta dika tou, afou polles fores tha xreiastei na sunergastei me allous. Isws kapoia stigmh na ginei ena tutorial panw se debugging techniques genika. Pros to paron as grafoume edw "exupnes" askhsoules( polles fores einai dika mas lathh Razz

) pou tha protrepoun tous upoloipous na vriskoun thn aitia tou lathous kai na diorthwnoun ton kwdika. Pisteuw einai mia wraia askhsoula otan variesai na grafeis kwdika na exaskeis to mualo sou etsi.
Loipon xekiname me ton parakatw aplo kwdika:

Code:

include <stdio.h>

int main(void){

struct data{

char *first_name;
char *last_name;
}data;

puts("Give me your name, please:");
scanf("%s",data.first_name);
printf("Hello %s, now give me your last name:\n",data.first_name);
scanf("%s",data.last_name);
printf("Name: %s and Last name: %s \n",data.first_name,data.last_name);

return 0;
}

Ena sample output einai auto:

Code:

Give me your name, please:
Odusseas
Hello Odusseas, now give me your last name:
Papadopoulos
Segmentation fault

To lathos telika to vlepei o gcc. Alla tis ptaiei? Ti prepei na ginei?

Brolly · Admin Posts: 3 Join date: 2008-04-24

Na desmeusoume mnhmh gia to onoma/epi8eto

Code:

data.first_name=(char*)malloc(20*sizeof(char));
data.last_name=(char*)malloc(20*sizeof(char));

m1cRo · Posts: 9 Join date: 2008-04-30

Code:

include <stdio.h>

int main(void){

struct data{

char first_name[10];
char last_name[10];
}data;

puts("Give me your name, please:");
scanf("%9s",data.first_name);
printf("Hello %s, now give me your last name:\n",data.first_name);
scanf("%9s",data.last_name);
printf("Name: %s and Last name: %s \n",data.first_name,data.last_name);

return 0;
}

m1cRo · Posts: 9 Join date: 2008-04-30

Brolly wrote:

Na desmeusoume mnhmh gia to onoma/epi8eto

Code:

data.first_name=(char*)malloc(20*sizeof(char));
data.last_name=(char*)malloc(20*sizeof(char));

Einai ok apla meta prepei na thn kaneis free .
Episis an kapios patisei parapano apo 20 xaraktires pali exeis overflow .

Spoofer · Broadcaster Posts: 14 Join date: 2008-04-29

Cool, m'aresei opws paei.. epomenws poia einai h veltisth lush?
Mhn xexname oti an einai >20 den tha einai onoma ara thelei enan effective elegxo megethous me analogo mhnuma.
As ton kanoume oso pio asfalh ginetai.. perimenw protaseis.

// edit: ok mperdeuthka me ton kwdika sou panw. Nomiza oti einai o dikos mou. Grafe kai kanena mhnuma re anthrwpe. cheers

m1cRo · Posts: 9 Join date: 2008-04-30

Spoofer wrote:

Cool, m'aresei opws paei.. epomenws poia einai h veltisth lush?
Mhn xexname oti an einai >20 den tha einai onoma ara thelei enan effective elegxo megethous me analogo mhnuma.
As ton kanoume oso pio asfalh ginetai.. perimenw protaseis.

Ma egrapsa mia lysh apo panw .
an thelete na ekxoreite mnimh tote use malloc kai free .

Spoofer · Broadcaster Posts: 14 Join date: 2008-04-29

m1cRo wrote:

Code:

include <stdio.h>

int main(void){

struct data{

char first_name[10];
char last_name[10];
}data;

puts("Give me your name, please:");
scanf("%9s",data.first_name);
printf("Hello %s, now give me your last name:\n",data.first_name);
scanf("%9s",data.last_name);
printf("Name: %s and Last name: %s \n",data.first_name,data.last_name);

return 0;
}

m1cRo aytos o kwdikas den douleuei etsi opws theloume. An dwsw sthn prwth scanf 15 'a' tote to periexomeno tou first_name tha einai ta 9 prwta 'a' kai tou last_name ta upoloipa 6.
To thema einai oti prepei na emfanizei mhnuma lathous se periptwsh pou kapoio apo ta 2 einai megalutero enos logikou megethous ( estw 15) kai tautoxrona na mhn ginetai kai overflow.
Perimenw kati oloklhrwmeno.

christaker · Posts: 1 Join date: 2008-05-06

Code:

#include <stdio.h>
#include <string.h>

main()
{
struct data{
   char first_name[15];
   char last_name[15];
}data;

puts("Give me your name, please:");
while(scanf("%s",data.first_name)&&strlen(data.first_name)>15){
   puts("Name must be under 16 char.\nGive me your name please : ");};

printf("Hello %s, now give me your last name:\n",data.first_name);
while(scanf("%s",data.last_name)&&strlen(data.last_name)>15){
   puts("Last name must be under 16 char.\nGive me your last name please : ");};
printf("Name: %s and Last name: %s \n",data.first_name,data.last_name);

return 0;
}

Etsi einai dekto? An mou epitrepetai vevaia na kanw include to string.h ....... Smile

Spoofer · Broadcaster Posts: 14 Join date: 2008-04-29

christaker wrote:

Code:

#include <stdio.h>
#include <string.h>

main()
{
struct data{
   char first_name[15];
   char last_name[15];
}data;

puts("Give me your name, please:");
while(scanf("%s",data.first_name)&&strlen(data.first_name)>15){
   puts("Name must be under 16 char.\nGive me your name please : ");};

printf("Hello %s, now give me your last name:\n",data.first_name);
while(scanf("%s",data.last_name)&&strlen(data.last_name)>15){
   puts("Last name must be under 16 char.\nGive me your last name please : ");};
printf("Name: %s and Last name: %s \n",data.first_name,data.last_name);

return 0;
}

Etsi einai dekto? An mou epitrepetai vevaia na kanw include to string.h ....... Smile

christaker wraia prospatheia kai fusika mporeis na kaneis xrhsh tou string.h. Ti exeis omws na peis gi'auto:

Code:

Give me your name, please:
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
Name must be under 16 char.
Give me your name please :
as
Hello as, now give me your last name:
as
Name: as and Last name: as
Segmentation fault

ps: Ti mporei na ginei?