Question

What is wrong if we push the strings into vector like this:

globalstructures->schema.columnnames.push_back("id");

When i am applied valgrind on my code it is showing

possibly lost of 27 bytes in 1 blocks are possibly lost in loss record 7 of 19.

like that in so many places it is showing possibly lost…..because of this the allocations and frees are not matching….which is resulting in some strange error like

malloc.c:No such file or directory

Although I am using calloc for allocation of memory everywhere in my code i am getting warnings like

Syscall param write(buf) points to uninitialised byte(s)

The code causing that error is

  datapage *dataPage=(datapage *)calloc(1,PAGE_SIZE);               
  writePage(dataPage,dataPageNumber); 
             
                     
  int writePage(void *buffer,long pagenumber)                 
  {
    int fd;
    fd=open(path,O_WRONLY, 0644);

     if (fd < 0)
        return -1;

    lseek(fd,pagenumber*PAGE_SIZE,SEEK_SET);

     if(write(fd,buffer,PAGE_SIZE)==-1)
    return false;


      close(fd);
      return true;
  }

Exact error which i am getting when i am running through gdb is …

Breakpoint 1, getInfoFromSysColumns (tid=3, numColumns=@0x7fffffffdf24: 1, typesVector=…, constraintsVector=…, lengthsVector=…,
columnNamesVector=…, offsetsVector=…) at dbheader.cpp:1080

Program received signal SIGSEGV, Segmentation fault.

_int_malloc (av=0x7ffff78bd720, bytes=8) at malloc.c:3498
3498 malloc.c: No such file or directory.

When i run the same through valgrind it’s working fine…

Answer 1

Well,

malloc.c:No such file or directory

can occur while you are debugging using gdb and you use command “s” instead of “n” near malloc which essentially means you are trying to step into malloc, the source of which may not be not available on your Linux machine.

That is perhaps the same reason why it is working fine with valgrind.