I tried to call a hello.c from V (but it doen't work)

[serge-hulne]

• hello.h
  =====

int sayHello(const char *name);

• app.v:
  =====

#flag -L. 
#flag -lhello.o
#flag -I.

#include "hello.h"


fn C. sayHello(&char) int

fn main() {
	C.sayHello(c'Hello bob')
}

• hello.c
  ====

#include <stdio.h> 

int sayHello(const char *name) { 
    printf("Hello %s!\n", name);   
    return 0;  
}

• Error message:
  ==========

==================
tcc: error: library 'C:\Users\serge\.vmodules\cache\f6\f6253053a488f4fc2bc48c83b32fcfd2.module.main.o' not found
...
==================
(Use `v -cg` to print the entire error message)

builder error:
==================
C error. This should never happen.

This is a compiler bug, please report it using `v bug file.v`.

https://github.com/vlang/v/issues/new/choose

You can also use #help on Discord: https://discord.gg/vlang

• Data:
  ====

- Windows 11
- V 0.3.3 65d218e
- WinLibs

[JalonSolov]

I see one error in your source:

fn C. sayHello(&char) int

should not have a space between the C. and sayHello. It should be:

fn C.sayHello(&char) int

Also need to know the command lines used to compile the V and C code.

[serge-hulne]

• The space was a typo (there's no space, in fact).
• command to compile hello.c : gcc -c hello.c
• command to compile app.v : v .
  (where gcc is the one which comes with the WinLibs toolchain)

Is it possible that when I run v ., v calls another compiler?
PS: V itself was compiled using the WinLibs toolchain.

[JalonSolov]

Ok, the next problem is that you have

#flag -lhello.o

but, as stated in the V docs,

-l for adding C library names that you want to get linked

A plain .o file is not a library that can be linked. It needs to either be a .a (archive) if linking statically or .so (shared object) file for linking dynamically. Also, the #flag -l needs to only give the name without the extension.

[JalonSolov]

Alternatively, you can have V output a .c file, and let gcc compile both and link them together:

v -gc none -o app.c app.v
gcc app.c hello.c

This creates a.out. Running that gives you

$ ./a.out
Hello Hello bob!
$

[serge-hulne]

thanks @JalonSolov .

• I have modified app.v into:

#flag -L. 
#flag -lhello
#flag -I.

#include "hello.h"


fn C.sayHello(&char) int

fn main() {
	C.sayHello(c'Hello bob')
}

and I have compiled the sources with:

app.exe : app.v hello.so
	v -cg .

hello.so : hello.o
	gcc hello.o -shared -o hello.so

hello.o : hello.c
	 gcc -c -fPIC hello.c -o hello.o

clean :
	rm -f *.o *.so *.exe

and I now get the error:

PS C:\Users\serge\Documents\vue-tests\vue-tests-nomodules\webviewGTK_bindings\bindings_tests_V> make
gcc -c -fPIC hello.c -o hello.o
gcc hello.o -shared -o hello.so
v -cg .
C:/Users/serge/AppData/Local/Temp/v_0/bindings_tests_V.15427387826144072384.tmp.c:492: warning: WINVER redefined
C:/Users/serge/AppData/Local/Temp/v_0/bindings_tests_V.15427387826144072384.tmp.c:6808: warning: implicit declaration of function 'tcc_backtrace'
C:/Users/serge/AppData/Local/Temp/v_0/bindings_tests_V.15427387826144072384.tmp.c:7556: warning: assignment from incompatible pointer type
C:/Users/serge/AppData/Local/Temp/v_0/bindings_tests_V.15427387826144072384.tmp.c:7556: warning: assignment makes pointer from integer without a cast
C:/Users/serge/AppData/Local/Temp/v_0/bindings_tests_V.15427387826144072384.tmp.c:7556: warning: cast between pointer and integer of different size
tcc: error: library 'hello' not found
builder error:
==================
C error. This should never happen.

This is a compiler bug, please report it using `v bug file.v`.

https://github.com/vlang/v/issues/new/choose

You can also use #help on Discord: https://discord.gg/vlang

make: *** [makefile:2: app.exe] Error 1

I have also tried calling the library gcc hello.o -shared -o libhello.so, but I get the same result.

[Wajinn]

A plain .o file is not a library that can be linked. It needs to either be a .a (archive) if linking statically or .so (shared object) file for linking dynamically. Also, the #flag -l needs to only give the name without the extension.

The OP mentioned they are a Windows OS user. It would usually be .dll as oppose to .so.

[serge-hulne]

With the other approach (v to c and compile)

v -gc none -o app.c app.v
gcc app.c hello.c

I get another error message :

 gcc app.c hello.c
app.c: In function 'winapi_lasterr_str':
app.c:7250:195: warning: passing argument 5 of 'FormatMessageW' from incompatible pointer type [-Wincompatible-pointer-types]
 7250 |         voidptr res = FormatMessage(((FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM) | FORMAT_MESSAGE_IGNORE_INSERTS), NULL, err_msg_id, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT), &msgbuf, 0, NULL);
      |
                                                    ^~~~~~~
      |
                                                    |
      |
                                                    u16 ** {aka short unsigned int **}
In file included from c:\mingw64\x86_64-w64-mingw32\include\windows.h:70,
                 from app.c:496:
c:\mingw64\x86_64-w64-mingw32\include\winbase.h:1385:122: note: expected 'LPWSTR' {aka 'short unsigned int *'} but argument is of type 'u16 **' {aka
short unsigned int **'}
 1385 |   WINBASEAPI DWORD WINAPI FormatMessageW (DWORD dwFlags, LPCVOID lpSource, DWORD dwMessageId, DWORD dwLanguageId, LPWSTR lpBuffer, DWORD nSize, va_list *Arguments);
      |                                                                                                                   ~~~~~~~^~~~~~~~
app.c:7250:23: warning: initialization of 'voidptr' {aka 'void *'} from 'DWORD' {aka 'long unsigned int'} makes pointer from integer without a cast [-Wint-conversion]
 7250 |         voidptr res = FormatMessage(((FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM) | FORMAT_MESSAGE_IGNORE_INSERTS), NULL, err_msg_id, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT), &msgbuf, 0, NULL);
      |                       ^~~~~~~~~~~~~
c:/mingw64/bin/../lib/gcc/x86_64-w64-mingw32/12.2.0/../../../../x86_64-w64-mingw32/bin/ld.exe: c:/mingw64/bin/../lib/gcc/x86_64-w64-mingw32/12.2.0/../../../../x86_64-w64-mingw32/lib/../lib/libmingw32.a(lib64_libmingw32_a-crt0_c.o):crt0_c.c:(.text+0x46): undefined reference to `WinMain'
collect2.exe: error: ld returned 1 exit status

[getfile]

try ' v -cc gcc run app.v '
i think c code and v code must use same compiler if they work toghter

[serge-hulne]

Thanks!