drivers/firmware/efi/libstub/vsprintf.c:251:5: warning: no previous prototype for function 'efi_vsnprintf'

[kernel test robot <lkp@intel.com>]

tree:   https://github.com/intel-lab-lkp/linux/commits/Ard-Biesheuvel/x86-boot-Drop-pointless-re-implementation-of-panic/20260906-150819
head:   c551ec0edb0b057c415d5530905c288523a9bde8
commit: 00893af88a10aeb0548fcd863ad11e686a94957d efi/libstub: Output UTF-16 directly from vsnprintf()
date:   2 days ago
config: loongarch-allyesconfig (https://download.01.org/0day-ci/archive/20260909/202609090621.8xNKJOFX-lkp@intel.com/config)
compiler: clang version 22.1.8 (https://github.com/llvm/llvm-project ca7933e47d3a3451d81e72ac174dcb5aa28b59d1)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260909/202609090621.8xNKJOFX-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202609090621.8xNKJOFX-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> drivers/firmware/efi/libstub/vsprintf.c:251:5: warning: no previous prototype for function 'efi_vsnprintf' [-Wmissing-prototypes]
     251 | int efi_vsnprintf(efi_char16_t *buf, size_t size, const char *fmt, va_list ap,
         |     ^
   drivers/firmware/efi/libstub/vsprintf.c:251:1: note: declare 'static' if the function is not intended to be used outside of this translation unit
     251 | int efi_vsnprintf(efi_char16_t *buf, size_t size, const char *fmt, va_list ap,
         | ^
         | static 
   1 warning generated.


vim +/efi_vsnprintf +251 drivers/firmware/efi/libstub/vsprintf.c

   250	
 > 251	int efi_vsnprintf(efi_char16_t *buf, size_t size, const char *fmt, va_list ap,

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