Was it intended for the 'print' function of the pre-processor to generate the C code?

[icyselec]

This code usually fails to compile.

##[=[
print [[
static void greeting(void) {
	puts("Hello, world!");
}
]]
]=]

##[=[
cemit [[
	greeting();
]]
]=]

However, If you create the C code by giving the --print-code option, it leaves the following function definition at the begining of the source code. Example command line nelua --print-code test.nelua > output.c

static void greeting(void) {
	puts("Hello, world!");
}

And this code succeeds in C compiling.

One solution is to define the function as follows.

## perror = function (...) io.stderr:write(..., '\n') end
##[=[
-- no longer generate the C code.
perror [[
#define FOO BAR
]]
]=]

Is there no other solution that this for now?

[stefanos82]

The reason why it's not working as expected is because this code

##[=[
print [[
static void greeting(void) {
	puts("Hello, world!");
}
]]
]=]

takes place during preprocessing process.

In other words, you are using your preprocessor's print builtin function (that is Lua's), which you use to output (print) the C code as a raw multiline string message.

Your code

##[=[
cemit [[
	greeting();
]]
]=]

gets emitted inside your generated C code.

This code should not compile because it sees it as

static void greeting(void) {
  puts("Hello, world!");
}

/* ------------------------------ DIRECTIVES -------------------------------- */
/* Disable some warnings that the generated code can trigger. */
#if defined(__clang__) && __clang_major__ >= 3
  #pragma clang diagnostic ignored "-Wtype-limits"
  #pragma clang diagnostic ignored "-Wwrite-strings"
  #pragma clang diagnostic ignored "-Wunused"
  #pragma clang diagnostic ignored "-Wunused-parameter"
  #pragma clang diagnostic ignored "-Wmissing-field-initializers"
  #pragma clang diagnostic ignored "-Wparentheses-equality"
  #pragma clang diagnostic ignored "-Wtautological-compare"
  #pragma clang diagnostic ignored "-Wmissing-braces"
  #ifndef __cplusplus
    #pragma clang diagnostic ignored "-Wincompatible-pointer-types"
    #pragma clang diagnostic error   "-Wimplicit-function-declaration"
    #pragma clang diagnostic error   "-Wimplicit-int"
  #else
    #pragma clang diagnostic ignored "-Wnarrowing"
    #pragma clang diagnostic ignored "-Wc99-designator"
  #endif
#elif defined(__GNUC__) && __GNUC__ >= 5
  #pragma GCC diagnostic ignored "-Wtype-limits"
  #pragma GCC diagnostic ignored "-Wwrite-strings"
  #pragma GCC diagnostic ignored "-Wunused-parameter"
  #pragma GCC diagnostic ignored "-Wunused-value"
  #pragma GCC diagnostic ignored "-Wunused-variable"
  #pragma GCC diagnostic ignored "-Wunused-function"
  #pragma GCC diagnostic ignored "-Wunused-but-set-variable"
  #pragma GCC diagnostic ignored "-Wmissing-field-initializers"
  #ifndef __cplusplus
    #pragma GCC diagnostic ignored "-Wmissing-braces"
    #pragma GCC diagnostic ignored "-Wincompatible-pointer-types"
    #pragma GCC diagnostic ignored "-Wdiscarded-qualifiers"
    #pragma GCC diagnostic error   "-Wimplicit-function-declaration"
    #pragma GCC diagnostic error   "-Wimplicit-int"
  #else
    #pragma GCC diagnostic ignored "-Wnarrowing"
  #endif
#endif
#if defined(_WIN32) && !defined(_CRT_SECURE_NO_WARNINGS)
  #define _CRT_SECURE_NO_WARNINGS
#endif
/* Macro used to perform compile-time checks. */
#if __STDC_VERSION__ >= 201112L
  #define NELUA_STATIC_ASSERT _Static_assert
#elif __cplusplus >= 201103L
  #define NELUA_STATIC_ASSERT static_assert
#else
  #define NELUA_STATIC_ASSERT(x, y)
#endif
/* Macro used to get alignment of a type. */
#if __STDC_VERSION__ >= 201112L
  #define NELUA_ALIGNOF _Alignof
#elif __cplusplus >= 201103L
  #define NELUA_ALIGNOF alignof
#elif defined(__GNUC__)
  #define NELUA_ALIGNOF __alignof__
#elif defined(_MSC_VER)
  #define NELUA_ALIGNOF __alignof
#else
  #define NELUA_ALIGNOF(x)
#endif
/* Checks if Nelua and C agrees on pointer size. */
NELUA_STATIC_ASSERT(sizeof(void*) == 8 && NELUA_ALIGNOF(void*) == 8, "Nelua and C disagree on pointer size or alignment");
/* Enable 64 bit offsets for stdio APIs. */
#if !defined(_FILE_OFFSET_BITS) && __SIZEOF_LONG__ >= 8
  #define _FILE_OFFSET_BITS 64
#endif
/* Enable POSIX APIs in included headers. */
#if !defined(_POSIX_C_SOURCE) && !defined(_XOPEN_SOURCE) && !defined(_GNU_SOURCE) && !defined(_DEFAULT_SOURCE)
  #if defined(__gnu_linux__)
    #define _GNU_SOURCE
  #else
    #define _XOPEN_SOURCE 600
  #endif
#endif
/* ------------------------------ DECLARATIONS ------------------------------ */
static int nelua_main(int argc, char** argv);
/* ------------------------------ DEFINITIONS ------------------------------- */
int nelua_main(int argc, char** argv) {
  greeting();
  return 0;
}
int main(int argc, char** argv) {
  return nelua_main(argc, argv);
}

and if you attempt to run it, you should expect to see something like

static void greeting(void) {
  puts("Hello, world!");
}

/home/stefanos/.cache/nelua/tmp.c: In function ‘nelua_main’:
/home/stefanos/.cache/nelua/tmp.c:83:3: error: implicit declaration of function ‘greeting’ [-Wimplicit-function-declaration]
   83 |   greeting();
      |   ^~~~~~~~
error: C compilation for '/home/stefanos/.cache/nelua/tmp' failed

shell returned 1

Now, if you replace your print with cemitdefn and above ##[[ you add ##cinclude '<stdio.h>', in other words now your code should look like

## cinclude '<stdio.h>'

##[=[
cemitdefn [[
static void greeting(void) {
  puts("Hello, world!");
}
]]
]=]

##[=[
cemit [[
  greeting();
]]
]=]

with --print-code you should expect to see

/* ------------------------------ DIRECTIVES -------------------------------- */
/* Disable some warnings that the generated code can trigger. */
#if defined(__clang__) && __clang_major__ >= 3
  #pragma clang diagnostic ignored "-Wtype-limits"
  #pragma clang diagnostic ignored "-Wwrite-strings"
  #pragma clang diagnostic ignored "-Wunused"
  #pragma clang diagnostic ignored "-Wunused-parameter"
  #pragma clang diagnostic ignored "-Wmissing-field-initializers"
  #pragma clang diagnostic ignored "-Wparentheses-equality"
  #pragma clang diagnostic ignored "-Wtautological-compare"
  #pragma clang diagnostic ignored "-Wmissing-braces"
  #ifndef __cplusplus
    #pragma clang diagnostic ignored "-Wincompatible-pointer-types"
    #pragma clang diagnostic error   "-Wimplicit-function-declaration"
    #pragma clang diagnostic error   "-Wimplicit-int"
  #else
    #pragma clang diagnostic ignored "-Wnarrowing"
    #pragma clang diagnostic ignored "-Wc99-designator"
  #endif
#elif defined(__GNUC__) && __GNUC__ >= 5
  #pragma GCC diagnostic ignored "-Wtype-limits"
  #pragma GCC diagnostic ignored "-Wwrite-strings"
  #pragma GCC diagnostic ignored "-Wunused-parameter"
  #pragma GCC diagnostic ignored "-Wunused-value"
  #pragma GCC diagnostic ignored "-Wunused-variable"
  #pragma GCC diagnostic ignored "-Wunused-function"
  #pragma GCC diagnostic ignored "-Wunused-but-set-variable"
  #pragma GCC diagnostic ignored "-Wmissing-field-initializers"
  #ifndef __cplusplus
    #pragma GCC diagnostic ignored "-Wmissing-braces"
    #pragma GCC diagnostic ignored "-Wincompatible-pointer-types"
    #pragma GCC diagnostic ignored "-Wdiscarded-qualifiers"
    #pragma GCC diagnostic error   "-Wimplicit-function-declaration"
    #pragma GCC diagnostic error   "-Wimplicit-int"
  #else
    #pragma GCC diagnostic ignored "-Wnarrowing"
  #endif
#endif
#if defined(_WIN32) && !defined(_CRT_SECURE_NO_WARNINGS)
  #define _CRT_SECURE_NO_WARNINGS
#endif
/* Macro used to perform compile-time checks. */
#if __STDC_VERSION__ >= 201112L
  #define NELUA_STATIC_ASSERT _Static_assert
#elif __cplusplus >= 201103L
  #define NELUA_STATIC_ASSERT static_assert
#else
  #define NELUA_STATIC_ASSERT(x, y)
#endif
/* Macro used to get alignment of a type. */
#if __STDC_VERSION__ >= 201112L
  #define NELUA_ALIGNOF _Alignof
#elif __cplusplus >= 201103L
  #define NELUA_ALIGNOF alignof
#elif defined(__GNUC__)
  #define NELUA_ALIGNOF __alignof__
#elif defined(_MSC_VER)
  #define NELUA_ALIGNOF __alignof
#else
  #define NELUA_ALIGNOF(x)
#endif
/* Checks if Nelua and C agrees on pointer size. */
NELUA_STATIC_ASSERT(sizeof(void*) == 8 && NELUA_ALIGNOF(void*) == 8, "Nelua and C disagree on pointer size or alignment");
/* Enable 64 bit offsets for stdio APIs. */
#if !defined(_FILE_OFFSET_BITS) && __SIZEOF_LONG__ >= 8
  #define _FILE_OFFSET_BITS 64
#endif
/* Enable POSIX APIs in included headers. */
#if !defined(_POSIX_C_SOURCE) && !defined(_XOPEN_SOURCE) && !defined(_GNU_SOURCE) && !defined(_DEFAULT_SOURCE)
  #if defined(__gnu_linux__)
    #define _GNU_SOURCE
  #else
    #define _XOPEN_SOURCE 600
  #endif
#endif
#include <stdio.h>
/* ------------------------------ DECLARATIONS ------------------------------ */
static int nelua_main(int argc, char** argv);
/* ------------------------------ DEFINITIONS ------------------------------- */
static void greeting(void) {
  puts("Hello, world!");
}
int nelua_main(int argc, char** argv) {
  greeting();
  return 0;
}
int main(int argc, char** argv) {
  return nelua_main(argc, argv);
}

which produces the right message output Hello, world!.