Warning: No Previous Declaration - C++ [closed]

Question

Closed. This question does not meet Stack Overflow guidelines. It is not currently accepting answers.

Closed 12 years ago.

Questions asking for code must demonstrate a minimal understanding of the problem being solved. Include attempted solutions, why they didn't work, and the expected results. See also: Stack Overflow question checklist
Questions concerning problems with code you've written must describe the specific problem — and include valid code to reproduce it — in the question itself. See SSCCE.org for guidance.

I am stumped about the cause of this:

recorders/r5000device.cpp: In function ‘unsigned int r5000_device_tspacket_handler(unsigned char*, int, void*)’:
recorders/r5000device.cpp:34:14: warning: no previous declaration for ‘unsigned int r5000_device_tspacket_handler(unsigned char*, int, void*)’ [-Wmissing-declarations]
 unsigned int r5000_device_tspacket_handler(unsigned char *tspacket, int len, void *callback_data)
          ^
recorders/r5000device.cpp: In function ‘void r5000_msg(char*)’:
recorders/r5000device.cpp:44:6: warning: no previous declaration for ‘void r5000_msg(char*)’ [-Wmissing-declarations]
 void r5000_msg(char * msg)
  ^

egur · Accepted Answer · 2013-11-26 22:38:30Z

12

You have the compile flag -Wmissing-declarations set. The compiler wants to see declarations (prototypes - usually in headers) for all function. Just add the missing headers or declare the prototype at the top of the file.

answered Nov 26, 2013 at 22:38

egur

8,0102 gold badges30 silver badges47 bronze badges

Sign up to request clarification or add additional context in comments.

4 Comments

user3033518 Over a year ago

I tried (as below), but I must be doing something wrong.

egur Over a year ago

Make sure you include the header file. If this function is local to the file, declare it as static. BTW the Intel compiler gives a similar warning

user3033518 Over a year ago

Thanks egur. I solved it by putting in r5000device.h: `unsigned int r5000_device_tspacket_handler(unsigned char tspacket, int len, void *callback_data); void r5000_msg(char);' so you'd nailed it. It was a big hassle determining whether I needed #ifndef or some other dressing up, but it turns out I just needed the bare declarations.

ricab Over a year ago

can also put the function into anonymous namespace

Community · Accepted Answer · 2017-05-23 12:28:47Z

0

Free functions in C++ need to be declared in a header file as well as defined in a .cpp file. How do you define a global function in C++?

edited May 23, 2017 at 12:28

CommunityBot

11 silver badge

answered Nov 26, 2013 at 22:37

Tim Pierce

5,7041 gold badge18 silver badges31 bronze badges

1 Comment

user3033518 Over a year ago

It doesn't work as your link says it should. In r5000device.h I put at the top:

#ifndef r5000_device_tspacket_handler #define r5000_device_tspacket_handler unsigned int r5000_device_tspacket_handler(unsigned char *tspacket, int len, void *callback_data); #endif

... but it responds:

In file included from videosource.cpp:39:0: recorders/r5000device.h:9:15: error: expected unqualified-id before ‘unsigned’  unsigned int r5000_device_tspacket_handler(unsigned char *tspacket, int len, void *callback_data);

Collectives™ on Stack Overflow

Warning: No Previous Declaration - C++ [closed]

2 Answers 2

4 Comments

1 Comment

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

4 Comments

1 Comment

Linked

Related