# 14 Warning Messages

- Introduction
- Warning message suppression
- Enabling extra warnings
- Issuing a warning message
- Symbolic symbols
- Commentary
- Warnings as errors
- Message output format
- Warning number reference
  - Deprecated features (100-199)
  - Preprocessor (200-299)
  - C/C++ Parser (300-399)
  - Types and typemaps (400-499)
  - Code generation (500-599)
  - Language module specific (800-899)
  - User defined (900-999)
- History

## 14.1 Introduction

During compilation, SWIG may generate a variety of warning messages. For example:

    example.i:16: Warning 501: Overloaded declaration ignored.  bar(double)
    example.i:15: Warning 501: Previous declaration is bar(int)

Typically, warning messages indicate non-fatal problems with the input where the generated wrapper code will probably compile, but it may not work like you expect.

## 14.2 Warning message suppression

All warning messages have a numeric code that is shown in the warning message itself. To suppress the printing of a warning message, a number of techniques can be used. First, you can run SWIG with the `-w` command line option. For example:

    % swig -python -w501 example.i
    % swig -python -w501,505,401 example.i

Alternatively, warnings can be suppressed by inserting a special preprocessor pragma into the input file:

    %module example
    #pragma SWIG nowarn=501
    #pragma SWIG nowarn=501,505,401

Finally, code-generation warnings can be disabled on a declaration by declaration basis using the `%warnfilter` directive. For example:

    %module example
    %warnfilter(501) foo;
    ...
    int foo(int);
    int foo(double);              // Silently ignored.

The `%warnfilter` directive has the same semantics as other declaration modifiers like `%rename`, `%ignore` and `%feature`, see the %feature directive section. For example, if you wanted to suppress a warning for a method in a class hierarchy, you could do this:

    %warnfilter(501) Object::foo;
    class Object {
    public:
       int foo(int);
       int foo(double);      // Silently ignored
       ...
    };

    class Derived : public Object {
    public:
       int foo(int);
       int foo(double);      // Silently ignored
       ...
    };

Warnings can be suppressed for an entire class by supplying a class name. For example:

    %warnfilter(501) Object;

    class Object {
    public:
       ...                      // All 501 warnings ignored in class
    };

There is no option to suppress all SWIG warning messages. The warning messages are there for a reason---to tell you that something may be broken in your interface. Ignore the warning messages at your own peril.

## 14.3 Enabling extra warnings

Some warning messages are disabled by default and are generated only to provide additional diagnostics. These warnings can be turned on using the `-Wextra` option. For example:

    % swig -Wextra -python example.i

To selectively turn on extra warning messages, you can use the directives and options in the previous section--simply add a "+" to all warning numbers. For example:

    % swig -w+309,+452 example.i

or in your interface file use either

    #pragma SWIG nowarn=+309,+452

or

    %warnfilter(+309,+452) foo;

Note: selective enabling of warnings with `%warnfilter` overrides any global settings you might have made using `-w` or `#pragma`.

You can of course also enable all warnings and suppress a select few, for example:

    % swig -Wextra -w309,452 example.i

The warnings on the right take precedence over the warnings on the left, so in the above example `-Wextra` adds numerous warnings including 452, but then `-w309,452` overrides this and so 452 is suppressesed.

If you would like all warnings to appear, regardless of the warning filters used, then use the `-Wall` option. The `-Wall` option also turns on the extra warnings that `-Wextra` adds, however, it is subtely different. When `-Wall` is used, it also disables all other warning filters, that is, any warnings suppressed or added in `%warnfilter`, `#pragma SWIG nowarn` or the `-w` option.

## 14.4 Issuing a warning message

Warning messages can be issued from an interface file using a number of directives. The `%warn` directive is the most simple:

    %warn "900:This is your last warning!"

All warning messages are optionally prefixed by the warning number to use. If you are generating your own warnings, make sure you don't use numbers defined in the table at the end of this section.

The `%ignorewarn` directive is the same as `%ignore` except that it issues a warning message whenever a matching declaration is found. For example:

    %ignorewarn("362:operator= ignored") operator=;

Warning messages can be associated with typemaps using the `warning` attribute of a typemap declaration. For example:

    %typemap(in, warning="901:You are really going to regret this") blah * {
       ...
    }

In this case, the warning message will be printed whenever the typemap is actually used.

## 14.5 Symbolic symbols

The `swigwarn.swg` file that is installed with SWIG contains symbol constants that could also be used in `%warnfilter` and `#pragma SWIG nowarn`. For example this file contains the following line:

    %define SWIGWARN_TYPE_UNDEFINED_CLASS 401 %enddef

so `SWIGWARN_TYPE_UNDEFINED_CLASS` could be used instead of 401, for example:

    #pragma SWIG nowarn=SWIGWARN_TYPE_UNDEFINED_CLASS

or

    %warnfilter(SWIGWARN_TYPE_UNDEFINED_CLASS) Foo;

## 14.6 Commentary

The ability to suppress warning messages is really only provided for advanced users and is not recommended in normal use. You are advised to modify your interface to fix the problems highlighted by the warnings wherever possible instead of suppressing warnings.

Certain types of SWIG problems are errors. These usually arise due to parsing errors (bad syntax) or semantic problems for which there is no obvious recovery. There is no mechanism for suppressing error messages.

## 14.7 Warnings as errors

Warnings can be handled as errors by using the `-Werror` command line option. This will cause SWIG to exit with a non successful exit code if a warning is encountered.

## 14.8 Message output format

The output format for both warnings and errors can be selected for integration with your favourite IDE/editor. Editors and IDEs can usually parse error messages and if in the appropriate format will easily take you directly to the source of the error. The standard format is used by default except on Windows where the Microsoft format is used by default. These can be overridden using command line options, for example:

    $ swig -python -Fstandard example.i
    example.i:4: Syntax error in input.
    $ swig -python -Fmicrosoft example.i
    example.i(4) : Syntax error in input.

## 14.9 Warning number reference

### 14.9.1 Deprecated features (100-199)

- 101. Deprecated `%extern` directive.
- 102. Deprecated `%val` directive.
- 103. Deprecated `%out` directive.
- 104. Deprecated `%disabledoc` directive.
- 105. Deprecated `%enabledoc` directive.
- 106. Deprecated `%doconly` directive.
- 107. Deprecated `%style` directive.
- 108. Deprecated `%localstyle` directive.
- 109. Deprecated `%title` directive.
- 110. Deprecated `%section` directive.
- 111. Deprecated `%subsection` directive.
- 112. Deprecated `%subsubsection` directive.
- 113. Deprecated `%addmethods` directive.
- 114. Deprecated `%readonly` directive.
- 115. Deprecated `%readwrite` directive.
- 116. Deprecated `%except` directive.
- 117. Deprecated `%new` directive.
- 118. Deprecated `%typemap(except)`.
- 119. Deprecated `%typemap(ignore)`.
- 120. Deprecated command line option (-runtime, -noruntime).
- 121. Deprecated `%name` directive.

### 14.9.2 Preprocessor (200-299)

- 201. Unable to find 'filename'.
- 202. Could not evaluate 'expr'.

### 14.9.3 C/C++ Parser (300-399)

- 301. `class` keyword used, but not in C++ mode.
- 302. Identifier 'name' redefined (ignored).
- 303. `%extend` defined for an undeclared class 'name'.
- 304. Unsupported constant value (ignored).
- 305. Bad constant value (ignored).
- 306. 'identifier' is private in this context.
- 307. Can't set default argument value (ignored)
- 308. Namespace alias 'name' not allowed here. Assuming 'name'
- 309. [private | protected] inheritance ignored.
- 310. Template 'name' was already wrapped as 'name' (ignored)
- 312. Unnamed nested class not currently supported (ignored).
- 313. Unrecognized extern type "name" (ignored).
- 314. 'identifier' is a lang keyword.
- 315. Nothing known about 'identifier'.
- 316. Repeated %module directive.
- 317. Specialization of non-template 'name'.
- 318. Instantiation of template 'name' is ambiguous, instantiation templ used, instantiation templ ignored.
- 319. No access specifier given for base class name (ignored).
- 320. Explicit template instantiation ignored.
- 321. identifier conflicts with a built-in name.
- 322. Redundant redeclaration of 'name'.
- 323. Recursive scope inheritance of 'name'.
- 324. Named nested template instantiations not supported. Processing as if no name was given to %template().
- 325. Nested class not currently supported (name ignored).
- 350. operator new ignored.
- 351. operator delete ignored.
- 352. operator+ ignored.
- 353. operator- ignored.
- 354. operator* ignored.
- 355. operator/ ignored.
- 356. operator% ignored.
- 357. operator^ ignored.
- 358. operator& ignored.
- 359. operator| ignored.
- 360. operator~ ignored.
- 361. operator! ignored.
- 362. operator= ignored.
- 363. operator< ignored.
- 364. operator> ignored.
- 365. operator+= ignored.
- 366. operator-= ignored.
- 367. operator*= ignored.
- 368. operator/= ignored.
- 369. operator%= ignored.
- 370. operator^= ignored.
- 371. operator&= ignored.
- 372. operator|= ignored.
- 373. operator<< ignored.
- 374. operator>>ignored.
- 375. operator<<= ignored.
- 376. operator>>= ignored.
- 377. operator== ignored.
- 378. operator!= ignored.
- 379. operator<= ignored.
- 380. operator>= ignored.
- 381. operator&& ignored.
- 382. operator|| ignored.
- 383. operator++ ignored.
- 384. operator-- ignored.
- 385. operator, ignored.
- 386. operator-<* ignored.
- 387. operator-< ignored.
- 388. operator() ignored.
- 389. operator[] ignored.
- 390. operator+ ignored (unary).
- 391. operator- ignored (unary).
- 392. operator* ignored (unary).
- 393. operator& ignored (unary).
- 394. operator new[] ignored.
- 395. operator delete[] ignored.

### 14.9.4 Types and typemaps (400-499)

- 401. Nothing known about class 'name'. Ignored.
- 402. Base class 'name' is incomplete.
- 403. Class 'name' might be abstract.
- 450. Deprecated typemap feature ($source/$target).
- 451. Setting const char * variable may leak memory.
- 452. Reserved
- 453. Can't apply (pattern). No typemaps are defined.
- 460. Unable to use type type as a function argument.
- 461. Unable to use return type type in function name.
- 462. Unable to set variable of type type.
- 463. Unable to read variable of type type.
- 464. Unsupported constant value.
- 465. Unable to handle type type.
- 466. Unsupported variable type type.
- 467. Overloaded declaration not supported (no type checking rule for 'type')
- 468. No 'throw' typemap defined for exception type type
- 469. No or improper directorin typemap defined for type
- 470. Thread/reentrant unsafe wrapping, consider returning by value instead.
- 471. Unable to use return type type in director method
- 474. Method method usage of the optimal attribute ignored in the out typemap as the following cannot be used to generate optimal code: code
- 475. Multiple calls to method might be generated due to optimal attribute usage in the out typemap.

### 14.9.5 Code generation (500-599)

- 501. Overloaded declaration ignored. decl. Previous declaration is decl.
- 502. Overloaded constructor ignored. decl. Previous declaration is decl.
- 503. Can't wrap 'identifier' unless renamed to a valid identifier.
- 504. Function name must have a return type.
- 505. Variable length arguments discarded.
- 506. Can't wrap varargs with keyword arguments enabled.
- 507. Adding native function name not supported (ignored).
- 508. Declaration of 'name' shadows declaration accessible via operator->(), previous declaration of'declaration'.
- 509. Overloaded method declaration effectively ignored, as it is shadowed by declaration.
- 510. Friend function 'name' ignored.
- 511. Can't use keyword arguments with overloaded functions.
- 512. Overloaded method declaration ignored, using non-const method declaration instead.
- 513. Can't generate wrappers for unnamed struct/class.
- 514.
- 515.
- 516. Overloaded method declaration ignored, using declaration instead.
- 517.
- 518. Portability warning: File file1 will be overwritten by file2 on case insensitive filesystems such as Windows' FAT32 and NTFS unless the class/module name is renamed.
- 519. %template() contains no name. Template method ignored: declaration

### 14.9.6 Language module specific (800-899)

- 801. Wrong name (corrected to 'name'). (Ruby).

- 810. No jni typemap defined for type (Java).
- 811. No jtype typemap defined for type (Java).
- 812. No jstype typemap defined for type (Java).
- 813. Warning for classname: Base baseclass ignored. Multiple inheritance is not supported in Java. (Java).
- 814.
- 815. No javafinalize typemap defined for type (Java).
- 816. No javabody typemap defined for type (Java).
- 817. No javaout typemap defined for type (Java).
- 818. No javain typemap defined for type (Java).
- 819. No javadirectorin typemap defined for type (Java).
- 820. No javadirectorout typemap defined for type (Java).
- 821.
- 822. Covariant return types not supported in Java. Proxy method will return basetype (Java).
- 823. No javaconstruct typemap defined for type (Java).
- 824. Missing JNI descriptor in directorin typemap defined for type (Java).

- 830. No ctype typemap defined for type (C#).
- 831. No cstype typemap defined for type (C#).
- 832. No cswtype typemap defined for type (C#).
- 833. Warning for classname: Base baseclass ignored. Multiple inheritance is not supported in C#. (C#).
- 834.
- 835. No csfinalize typemap defined for type (C#).
- 836. No csbody typemap defined for type (C#).
- 837. No csout typemap defined for type (C#).
- 838. No csin typemap defined for type (C#).
- 839.
- 840.
- 841.
- 842. Covariant return types not supported in C#. Proxy method will return basetype (C#).
- 843. No csconstruct typemap defined for type (C#).
- 844. C# exception may not be thrown - no $excode or excode attribute in typemap typemap. (C#).
- 845. Unmanaged code contains a call to a SWIG_CSharpSetPendingException method and C# code does not handle pending exceptions via the canthrow attribute. (C#).

- 870. Warning for classname: Base baseclass ignored. Multiple inheritance is not supported in PHP.
- 871. Unrecognized pragma pragma. (Php).

### 14.9.7 User defined (900-999)

These numbers can be used by your own application.

## 14.10 History

The ability to control warning messages was first added to SWIG-1.3.12.