free

问题 I have allocated memory using malloc() in embedded Linux (around 10 MB). And checked the free memory it was 67080 kB but even after freeing it using free() it remains the same. It is only after the application is terminated the memory is available again. Does free() not make the freed memory available to the system, if so how to make it available. 回答1: Does free() not make the freed memory available to the system. No, usually not. malloc() normally requests memory from the OS by the low level

来源： https://stackoverflow.com/questions/44271967/valgrind-shows-more-memory-allocated-than-actually-is

来源： https://stackoverflow.com/questions/44271967/valgrind-shows-more-memory-allocated-than-actually-is

问题 I came across an issue which I could not resolve. My question is, if I used malloc to allocate memory and then memory block is delete using delete ? The general thumb rule is If we allocate memory using malloc , it should be deleted using free . If we allocate memory using new , it should be deleted using delete . Now, in order to check what happens if we do the reverse, I wrote a small code. #include<iostream> #include<cstdio> #include<cstdlib> using namespace std; class A { int p=10; public

问题 I came across an issue which I could not resolve. My question is, if I used malloc to allocate memory and then memory block is delete using delete ? The general thumb rule is If we allocate memory using malloc , it should be deleted using free . If we allocate memory using new , it should be deleted using delete . Now, in order to check what happens if we do the reverse, I wrote a small code. #include<iostream> #include<cstdio> #include<cstdlib> using namespace std; class A { int p=10; public

问题 If you will look at the code of FreeAndNil procedure you will see: procedure FreeAndNil(var Obj); var Temp: TObject; begin Temp := TObject(Obj); Pointer(Obj) := nil; Temp.Free; end; What is the reason they assigning Nil to an object reference and only after this destroying it? Why not vice-versa? 回答1: I can think of two reasons for doing it this way round, neither of which seems at all compelling. Reason 1: to guarantee that the reference is set to nil in case an exception is raised The

问题 If you will look at the code of FreeAndNil procedure you will see: procedure FreeAndNil(var Obj); var Temp: TObject; begin Temp := TObject(Obj); Pointer(Obj) := nil; Temp.Free; end; What is the reason they assigning Nil to an object reference and only after this destroying it? Why not vice-versa? 回答1: I can think of two reasons for doing it this way round, neither of which seems at all compelling. Reason 1: to guarantee that the reference is set to nil in case an exception is raised The

问题 I have implemented a JNA bridge to FDK-AAC. Source code can be found in here When bench-marking my code, I can get hundreds of successful runs on the same input, and then occasionally a C-level crash that'll kill the entire process, causing a core-dump to be generated: Looking at the core dump, it looks like this: #1 0x00007f3e92e00f5d in __GI_abort () at abort.c:90 #2 0x00007f3e92e4928d in __libc_message (action=action@entry=do_abort, fmt=fmt@entry=0x7f3e92f70528 "*** Error in `%s': %s: 0x%s

问题 I am trying to free up char* acc at the end of this code: while (fgets(line, 300, fp)!=NULL) { char *tmp = strdup(line); char *acc = (char*) getfield(tmp, 2); //check if account number already exists if (acc != NULL){ if ((atoi(acc))== accNum){ return 1; } } free(tmp); free(acc); } getfield returns a const char* so I have casted it to char* , but an error arises from the pointer when I try to free() saying free(): invalid pointer . What am I doing wrong? Any help would be appreciated 来源：

问题 I have created a program that requires reading a CSV file that contains bank accounts and transaction history. To access certain information, I have a function getfield which reads each line token by token: const char* getfield(char* line, int num) { const char *tok; for (tok = strtok(line, ","); tok && *tok; tok = strtok(NULL, ",\n")) { if (!--num) return tok; } return NULL; } I use this later on in my code to access the account number (at position 2) and the transaction amount(position 4):