'Function not declared', while it clearly is...

Hi, I'm new here.

So I have been programming with C and GTK+, everything went fine, until I started to struggle with a single function that I've clearly defined, but GCC says otherwise.

The error:
Attachment 15004

Translation:
エラー：'open_func'が宣言されていません（この関数内での最初の使用）
Error: 'open_func' is not being declared (this function's inside was first used)

備考：未宣言の識別子は出現した各関数内で一回のみ報告されます
Note: Undeclared identifier that appears in each function's inside was being reported only once

Code:
main.c:

Code:

---

    // メニューシグナル。
    g_signal_connect(G_OBJECT(openMi), "activate",
        G_CALLBACK(open_func), (gpointer) window);

---

file.h

Code:

---

void open_func (GtkWidget *widget, gpointer window);

---

file.c

Code:

---

void open_func (GtkWidget *widget, gpointer window) {
    GtkWidget *dialogue;
    FILE * pFile;
   
    dialogue = gtk_file_chooser_dialog_new("Open file",
        GTK_WINDOW(window),
        GTK_FILE_CHOOSER_ACTION_OPEN,
        GTK_STOCK_CANCEL, GTK_RESPONSE_CANCEL,
        GTK_STOCK_OK, GTK_RESPONSE_OK,
        NULL);
   
    gtk_widget_show_all(dialogue);
   
    gtk_file_chooser_set_current_folder(GTK_FILE_CHOOSER(dialogue), g_get_home_dir());
    gint resp = gtk_dialog_run(GTK_DIALOG(dialogue));
   
    if (resp == GTK_RESPONSE_OK) {
        char *filename;
        filename = gtk_file_chooser_get_filename(GTK_FILE_CHOOSER(dialogue));
        pFile = fopen(filename, "r");
       
        if (pFile != NULL) {
            if (!readobjmodel (pFile, &objfile))
                exit (EXIT_FAILURE);
            renderobjmodel (&objfile);
        }
       
        g_free(filename);
       
        g_print("%s\n", gtk_file_chooser_get_filename(GTK_FILE_CHOOSER(dialogue)));
    }
    else {
        g_print("You pressed cancel.\n");
    }
   
    gtk_widget_destroy(dialogue);
}

---

By the way, excuse me if I made some mistakes, I'm Japanese.

Have you "included" the header file holding the function prototype in the same files as main.c and file.c?

Of course I did, both files include "file.h".

There are generally two reasons for this type of error.

1. The function has not been defined (generally a prototype) before it's used.

2. The other and more probable reason is the function name (either in definition or prototype) is spelled incorrectly, has the wrong return type, has the wrong amount of parameters types or is defined in a file that has no access to it's prototype.

What I would do is carefully look at each call to the function, check everything matches up with the prototype. I've never personally used the Gt setup with C, so that could also have a default reason that I am not familiar with. If none of the above works, look at the documentation of Gt and function definitions and see if there is a certain command or linker argument that needs implementing. If still nothing works, I am sure another poster may spot something.

Here are some possible ways it can go wrong.

1. Your include guards in file.h are not unique. You think you're including the file, but you're not.

2. You have some #define open_func another_name lying around somewhere, which changes the name you're looking for.

3. Your definition/declaration of open_func is surrounded by #if 0 .. #endif (or other preprocessor conditional which is false), thus removing it from visibility to the compiler.

4. In C++, it's in another namespace than the one you think it's in.

One thing to try is using the -E flag of the compiler. This just runs the pre-processor step.

Code:

---

$ gcc -E main.c > tmp
$ wc -l main.c tmp
  144 main.c
 23797 tmp

---

These are large files if you have lots of includes.

Currently, my code is on my Github account (private repository).
However, I can share you the full project files as well, so you can see that for yourself.
Should I do so?

If you feel that could help people look for the possible error then yes that could be an idea, but it's your personal work and it's up to you to feel comfortable with what you decide or decide not to show.

> Currently, my code is on my Github account (private repository).
Well doing 'git diff' between the last time it all worked and now would be a good start.

I solved the problem now.
Apparently, GCC didn't allow me to name my files "file.h" and "file.c".
I renamed them to "filez.h" and "filez.c", changed the "#include" lines to apply the name changes, and it worked!

You were most likely getting a file.h you didn't expect.

Code:

---

$ find /usr/include -name "file.h"
/usr/include/x86_64-linux-gnu/sys/file.h
/usr/include/x86_64-linux-gnu/libavutil/file.h
/usr/include/wx-3.0/wx/file.h
/usr/include/wx-3.0/wx/protocol/file.h

---

Beware of overly generic names like 'file' and 'test'

Use 'gcc -M prog.c' to see which header file(s) are actually resolved when compiling.