CODEWITHSUNDEEP
cprintf
Anne
Anne

Reputation: 123

How to do a sprintf on a uint32_t hexidecimal to and store it into a string?

I am running a timer to calculate the efficiency of my program and I need to output it to a hyperterminal. So, I need to do a sprintf on a uint32_t hexidecimal to store it into a string. But I keep getting an error on the %08X. So what should I use instead? I have tried using %ll, %lu but the warning is still there.

volatile char str_cycles=0;
volatile uint32_t total_cycles = 0x00ffffff - current_time;
sprintf(str_cycles, "%08X",total_cycles);

Can anyone help me with this?

Upvotes: 0

Views: 2849

Answers (3)

Jonathan Leffler
Jonathan Leffler

Reputation: 753495

You should be getting an error because str_cycles is shown as volatile char str_cycles; (a single character).

You should be using <inttypes.h> and:

char str_cycles[16];

snprintf(str_cycles, sizeof(str_cycles), "%08" PRIX32, total_cycles);

Generally, snprintf() should be preferred over sprintf(), but if you have enough space allocated it is perfectly OK to use sprintf().

I'm not convinced about the volatile qualifier either; it is your job to determine why you have that and whether it is correct and whether it matters. Generally, you do not want a volatile string; it makes using it unreliable. (This answer first omitted the volatile on str_cycles, then added it, and has now omitted it again.)

Upvotes: 4

TypeIA
TypeIA

Reputation: 17250

Cast to an int or unsigned first. This is the type expected by %X:

sprintf(str_cycles, "%08X", (unsigned) total_cycles);

Upvotes: 0

chux
chux

Reputation: 153338

Use fixed width print specifiers.

#include <inttypes.h>
char buf[9];
sprintf(buf, "%08" PRIX32,total_cycles);

Upvotes: 1

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