a basic test of c module

try to load .dll using .h header to supply definition signature

t.c

#include <stdio.h>

__declspec(dllexport) short add(short a, short b) {
  return a + b;
}


__declspec(dllexport) long long sub(long long a, long long b) {
  return a - b;
}

t.h

short
add(short a, short b) ;


long
long
sub
(long long
    a,
    long long b) ;

simple module crequire.lua:

t = {}
t['unsigned long long'] = 'L'
t['const wchar_t*'] = 'W'
t['unsigned short'] = 'S'
t['unsigned char'] = 'C'
t['unsigned long'] = 'J'
t['unsigned int'] = 'I'
t['const char*'] = 'Z'
t['long long'] = 'l'
t['uint32_t'] = 'I'
t['uint64_t'] = 'L'
t['wchar_t*'] = 'W'
t['uint16_t'] = 'S'
t['int16_t'] = 's'
t['int32_t'] = 'i'
t['int64_t'] = 'l'
t['double'] = 'd'
t['size_t'] = '#'
t['struct'] = '.'
t['char*'] = 'Z'
t['float'] = 'f'
t['short'] = 's'
t['union'] = 'u'
t['void*'] = 'p'
t['bool'] = 'B'
t['char'] = 'c'
t['long'] = 'j'
t['int'] = 'i'

trev = {}
for k,v in pairs(t) do
  trev[v] = trev[v] and (trev[v]..', or '..k)  or k
end


torder = {}
for k in pairs(t) do table.insert(torder,k) end
table.sort(torder, function(a,b) return #a>#b end)


function getdef(header, name)
   header = header:gsub('%s+', ' ')  -- also remove comment?
   wordboundary = '%f[_%w]'
   bracket = '%s-%b()'
   a,b = header:find(wordboundary..name..bracket)
   c = getbegin(header, b)
   returndef = header:sub(c, a-1) print('returndef', returndef)
   returntype = gettype(returndef)
   d = header:find('%(', a)
   arguments = header:sub(d+1, b-1)..','
   prev=0
   argutypest = {}
   for e in arguments:gmatch('(),') do
      argu = arguments:sub(prev+1, e)
      argut = gettype(argu)
      print(argu, argut)
      argutypest[#argutypest+1] = gettype(argu)
      prev=e
   end
   argutypes = table.concat(argutypest)
   return '('..argutypes..')'..returntype
end


function gettype(s)
   for _,k in ipairs(torder) do
      if s:find(k) then return t[k] end
   end
   return ''
end


function getbegin(s, b)
   -- begin at ;
   for i = b-1,1,-1 do
   if s:sub(i,i)==';' then b=i+1 break end end
   if b>a then b=1 end
   return b
end


function describe(s)
   local a,b = s:find('%b()')
   print'arguments:'
   if b-a==1 then print'  none'
   else for i=1,b-a-1 do print('',i,trev[s:sub(a+i,a+i)]) end end
   print'returns:'
   if b==#s then print'  none'
   else print('',trev[s:sub(#s)]) end
end


function crequire(dllname, funcname)
   mylib = cmodule.Library(dllname..'.dll')
   header = io.open(dllname..'.h'):read'a'
   def = getdef(header, funcname)
   mylib[funcname] = def
   print(funcname, def)
   describe(def)
   return mylib[funcname]
end

cmodule = require'c'
return crequire

and test in quickrt:

╭━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━╮
│ QuickRT - Powerful REPL for LuaRT  │
│ Copyright © 2025, Samir Tine       │
╰━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━╯

► crequire = require'crequire'

► add = crequire('t', 'add')
returndef       short
short a,        s
 short b,       s
add     (ss)s
arguments:
        1       int16_t, or short
        2       int16_t, or short
returns:
        int16_t, or short

► sub = crequire('t', 'sub')
returndef        long long
long long a,    l
 long long b,   l
sub     (ll)l
arguments:
        1       long long, or int64_t
        2       long long, or int64_t
returns:
        long long, or int64_t

► add(5,4)
9

► sub(5,4)
1

► sub(4,5)
4294967295

► c=require'c'
► c.longlong(sub(4,5)):tonumber()
0

► c.longlong(sub(5,4)):tonumber()
0

question,

uint32_t I or J ?
int32_t i or j ?
int B or i ?
or both are ok ?

is # size_t ?

I trid to set function return value to size_t, #
but it seems like # is not recognized

add(4,5)
>>> Unknown '#' signature character

and obviously difficulty lies in struct and union etc complcate types