#3644 mcs51: implicit promotion of 8-bit -> 16-bit in variadic args not working

[Oleg Endo]

compiling the following example with --model-large --std-sdcc2x -mmcs51 --stack-auto --nogcse

int main (void)
{
  printf ("bleh = %04x\n", (uint8_t)0xA3);
}

prints

bleh = a3c0

the expected output is

bleh = 00a3

rewriting the program as follows yields the expected result:

int main (void)
{
  uint8_t bleh = (uint8_t)0xA3;
  printf ("bleh = %04x\n", bleh);
}

SDCC version: 4.3.2 #0 (Linux) SVN r14340

[Maarten Brock]

This is deliberate. Using an explicit cast tells the compiler not to mess with promotions and pass the value as a single byte. This can be used with "%bc". You can add a second cast to int to get the expected result.

[Philipp Klaus Krause]

For details see section 3.5.12, "Omitting promotion on arguments of vararg function (does not apply to pdk13, pdk14, pdk15)" in the manual.
Having just had a look at it, that section could be a bit clearer though, as --std-sdccxx is the default.

[Oleg Endo]

Thanks for the clarification!