CODEWITHSUNDEEP
ctypescompilation
ransh
ransh

Reputation: 1702

64 bit variable is stored as 32-bit

I have some issue when compiling in ARM cross compiler with a variable of type unsigned long long

The variable represents partition size (~256GBytes). I expect it to be stored as 64-bit, but on printing it using %lld, or even trying to print it as Mega bytes (value/(1024*1024*1024)), I always see the only 32-bit of the real value.

Does anyone know why the compiler store it as 32-bits?

Edit:

My mistake, the value is set in C using the following calculation:

partition_size = st.f_bsize*st.f_frsize;
struct statvfs { unsigned long int f_bsize; unsigned long int f_frsize; ...}

The issue is that f_bsize and f_frsize are only 32 bits, and the compiler does not automatically cast them to 64bits! Casting solved this issue for me.

Upvotes: 1

Views: 312

Answers (2)

ransh
ransh

Reputation: 1702

My mistake........ the value is set in C using the following calcualtion:

partition_size = st.f_bsize*st.f_frsize;

struct statvfs { unsigned long int f_bsize; unsigned long int f_frsize;...}

The issue is that f_bsize & f_frsize are only 32 bits, and the compiler does not automatically cast them to 64bits!

Casting solved this issue for me.

Upvotes: 2

Gopi
Gopi

Reputation: 19864

The below code prints the whole 64 bits.Try printing it using %llu 

  main()
    {
    unsigned long long num = 4611111275421987987;
    printf("%llu\n",num);
    }

Upvotes: 1

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