Valgrind tool for GDB - gdb

Question

int main()
{
char *p;
p = malloc(10);
delete(p);
return;
}
what will be appropriate error detected by Valgrind?

Answer 1

First of all this code snippet gives two compilation errors,
In function ‘int main()’:
error: invalid conversion from ‘void*’ to ‘char*’ [-fpermissive]
p = malloc(10);
^
error: return-statement with no value, in function returning ‘int’ [- fpermissive]
return;
Correct the code with these changes,
Type cast while allocating memory using malloc, as shown here.
p = (char*) malloc(10);
The return type of main function is int, so change the return value accordingly, as mentioned here.
return 0; // Use return 0, instead of just return.
Before using delete operation, do a validity check on the pointer, as shown here.
if(p)
delete(p);
With the above changes, and upon successful compilation of the above code. Use the valgrind tool to run the above sample.
As such there is no issue in the code, so valgrind did not find any issue. Below is sample valgrind output.
Valgrind output:
==30050== Memcheck, a memory error detector
==30050== Copyright (C) 2002-2015, and GNU GPL'd, by Julian Seward et al.
==30050== Using Valgrind-3.12.0 and LibVEX; rerun with -h for copyright info
==30050== Command: ./valgrindtest
==30050==
main Start
==30050== Mismatched free() / delete / delete []
==30050== at 0x4C2C18D: operator delete(void*) (vg_replace_malloc.c:576)
==30050== by 0x4006E0: main (valgrindtest.cpp:16)
==30050== Address 0x5a1b040 is 0 bytes inside a block of size 10 alloc'd
==30050== at 0x4C2ABE3: malloc (vg_replace_malloc.c:299)
==30050== by 0x4006C2: main (valgrindtest.cpp:11)
==30050==
main End
==30050==
==30050== HEAP SUMMARY:
==30050== in use at exit: 0 bytes in 0 blocks
==30050== total heap usage: 1 allocs, 1 frees, 10 bytes allocated
==30050==
==30050== All heap blocks were freed -- no leaks are possible
==30050==
==30050== For counts of detected and suppressed errors, rerun with: -v
==30050== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 0 from 0)