# 19 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 (500-559)
  - Doxygen comments (560-599)
  - Language module specific (700-899)
  - User defined (900-999)
- History

## 19.1 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.

## 19.2 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.

## 19.3 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

Preprocessor warning 202 ("Could not evaluate expression expr.") was formally off by default and enabled by `-Wextra`, but since SWIG 4.1.0 this warning is on by default because suppressing it tends to hide genuine problems. If you really don't want to see it, you can suppress it with `-w202` or using `%warnfilter` as described below. Both will work with older versions of SWIG too.

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 suppressed.

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.

## 19.4 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 usage of $1_type $1_name") blah * {
      ...
    }

In this case, the warning message will be printed whenever the typemap is actually used and the special variables will be expanded as appropriate, for example:

    example.i:23: Warning 901: You are really going to regret this usage of blah * self
    example.i:24: Warning 901: You are really going to regret this usage of blah * stuff

## 19.5 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;

## 19.6 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.

## 19.7 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.

## 19.8 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(1).
    $ swig -python -Fmicrosoft example.i
    example.i(4) : Syntax error in input(1).

## 19.9 Warning number reference

### 19.9.1 Deprecated features (100-199)

None currently.

### 19.9.2 Preprocessor (200-299)

- 201. Unable to find filename.
- 202. Could not evaluate expression expr.
- 203. Both includeall and importall are defined: using includeall.
- 204. CPP #warning, "warning".
- 205. CPP #error, "error".
- 206. Unexpected tokens after #directive directive.

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

- 301. `class` keyword used, but not in C++ mode.
- 302. Redefinition of identifier 'name' as decl ignored.
- 303. `%extend` defined for an undeclared class 'name'.
- 304. Unsupported constant value (ignored).
- 305. Bad constant value (ignored).
- 308. Namespace alias 'name' not allowed here. Assuming 'name'
- 309. [private | protected] inheritance 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'.
- 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 identifier 'name' as decl ignored.
- 323. Recursive scope inheritance of 'name'.
- 324. Named nested template instantiations not supported. Processing as if no name was given to %template().
- 325. Nested kind not currently supported (name ignored).
- 326. Deprecated %extend name used - the kind name 'name' should be used instead of the typedef name 'name'.
- 327. Extern template ignored.
- 328. Value assigned to name not used due to limited parsing implementation.
- 329. Using declaration 'name' for inheriting constructors uses base 'name' which is not an immediate base of 'name'.
- 330. Template forward class 'name' cannot be used to instantiate a full template class with name 'name'.
- 331. Unsupported template nested class 'name' cannot be used to instantiate a full template class with name 'name'.
- 340. Lambda expressions and closures are not fully supported yet.
- 344. Unable to deduce decltype for 'expr'.
- 345. Unable to deduce auto return type for 'name' (ignored).
- 346. Unable to deduce auto type for variable '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.
- 396. operator*() ignored.
- 397. operator<=> delete[] ignored.

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

- 401. Nothing known about class 'name'. Ignored.
- 402. Base class 'name' is incomplete.
- 403. Class 'name' might be abstract.
- 404. Duplicate template instantiation of 'type' with name 'name' ignored, previous instantiation of 'type' with name 'name'.
- 405. Method with rvalue ref-qualifier name ignored.
- 406. Ignoring nspace setting (setting) for 'type', as it conflicts with the nspace setting (setting) for outer class 'type'
- 450. Reserved
- 451. Setting const char * variable may leak memory.
- 452. Reserved
- 453. Can't apply (pattern). No typemaps are defined.
- 454. Setting a pointer/reference variable may leak memory
- 455. Setting a const wchar_t * variable may leak memory.
- 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 (incomplete type checking rule - no precedence level in typecheck typemap 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
- 472. Overloaded method method with no explicit typecheck typemap for arg number of type 'type'. Dispatching calls to this method may not work correctly, see the 'Typemaps and Overloading' section in the Typemaps chapter of the SWIG documentation.
- 473. Returning a reference, pointer or pointer wrapper in a director method is not recommended.
- 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.
- 476. Initialization using std::initializer_list.
- 477. No directorthrows typemap defined for type
- 490. Fragment 'name' not found.

### 19.9.5 Code generation (500-559)

- 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. Ignored.
- 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
- 520. Base/Derived class 'classname1' of 'classname2' is not similarly marked as a smart pointer.
- 521. Illegal destructor name name. Ignored.
- 522. Use of an illegal constructor name 'name' in %extend is deprecated, the constructor name should be 'name'.
- 523. Use of an illegal destructor name 'name' in %extend is deprecated, the destructor name should be 'name'.
- 524. Experimental target language. Target language language specified by lang is an experimental language. See the 'Target Languages' section in the Introduction chapter of the SWIG documentation.
- 525. Destructor declaration is final, name cannot be a director class.
- 526. Using declaration declaration, with name 'name', is not actually using the method from declaration, with name 'name', as the names are different.
- 527. Deprecated target language. Target language language specified by lang is a deprecated language. It will be removed in the next release of SWIG unless a new maintainer steps forward to bring it up to at least experimental status. See the 'Target Languages' section in the Introduction chapter of the SWIG documentation.

### 19.9.6 Doxygen comments (560-599)

- 560: Unknown Doxygen command: command.
- 561: Unexpected end of Doxygen comment encountered.
- 562: Expected Doxygen command: command
- 563: Doxygen HTML error for tag tag: error text.
- 564: Error parsing Doxygen command command: error text. Command ignored."

### 19.9.7 Language module specific (700-899)

- 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).
- 825. "directorconnect" attribute missing in type "javaconstruct" typemap. (Java).
- 826. The nspace feature is used on 'type' without -package. The generated code may not compile as Java does not support types declared in a named package accessing types declared in an unnamed package. (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. (Php).
- 871. Unrecognized pragma pragma. (Php).

### 19.9.8 User defined (900-999)

These numbers can be used by your own application.

## 19.10 History

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