allocation et management de la memoire
Bonjour la communaute,
voila pour etre franc, une boite me demande de repondre a ces questions en moins de 24 heures et quelques soient les moyens utilises, je dois repondre correctement a toutes ces questions, meme si les reponses ne viennent pas de moi.
Si au moins l'un d'entre vous pouvez repondre a ces questions pour que je compare avec ce que je vais repondre de mon cote, ca serait super sympa ... j'ai besoin de reponses des plus professionnels d'entre-vous, car moi je suis seulement intermediaire.
Merci d'avance pour votre temps.
PS: j'ai eu deja quelques reponses dnas le forum C++(je pensai que c t du C++ au debut) donc les quesitons qui me bloquent le plus sont les dernieres 8, 9 et 10.
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Please be sure to mention MEMORY MANAGEMENT AND MEMORY ALLOCATION, specifically, in your answers.
Skill Assessment Sheet
Line
Contains
50
char *b, q, *r;
200
b = getbuf ();
201
q = *b;
212
R = anotherfunction (b);
213-2003
/* we want to use 'q' and 'r' here */
2000
char * getbuf ()
2001
{
2002
char buff [8];
2003-2050
/* unspecified buff defined here */
2051
return (char*) buff;
2052
}
1. What will be in variable 'q' after line 201 is executed? Under what conditions might this not be so?
The function "getbuf" has a memory allocation problem. Therefore the system memory management imply that b takes an undetermined value because of the return value of "getbuf". Then "q" will be undetermined because it is assigned to "*b".
2. Is there an alternative, but equivalent, way to write line 2000? If so, what is it?
Yes there are other ways to write it. For instance:
char *getbuf(void)
or
const char* getbuf()
3. Is getbuf() a reasonable function?
No it is not a reasonable function because it returns an adress of a local variable. As a result "getbuf" returns a pointer to a memory that is then desallocated by the memory management.
4. Will getbuf() execute at all?
It is the main problem of this program because "getbuf" would execute correctly. Indeed there are no memory allocation problems, it is just a memory management issue.
5. Please comment on line 2051.
It is useless to cast buff into a char* because it is an array by definition. Then it is not reasonable to return the adress of "buff" because it is a local variable about to be cleaned by memory management. Thus the pointer will be undetermined at the exit of "getbuf".
6. Is getbuf() good practice, and why?
"getbuf" is not good practice for all reasons given above. "buff" is a local variable of the fucntion. Thus the returned adress will point to something undetermined and the rest of program will suffer from this mistake.
7. What line not given should be provided for compilation?
A prototype of the function "getbuf" should be provided for compilation.
8. How, exactly, could one get a second 'char*' to use back from this function? Be specific in terms of the exact syntax needed. (That is, provide code.) Another way to state this question is how can this function be modified to return a 'char*' (that is, it maintains the same return type) from the function, and an additional 'char *' value in one function call. Please make sure that your answer will work even if the size of the char * desired is not known in the outside calling function. Avoid (do no use) C++ syntax. Include statement in called and calling functions. Use food programming practice.
9. For those candidates who know SQL: There is a table with gene_ids ('gid') and clone_ids ('cid'). Each gene only resides on a single clone and each clone may contain multiple genes. How do would you find how many genes are on each and every clone? Please provide the SQL.
10. What's the difference between system calls and library functions?
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