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Fix using exception in modules importing other modules

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Ensure that we have only a single SWIG_CException_Raise() function
across all modules instead of having per-module functions and, worse,
per-module PendingException variables, which resulted in compile-time
errors and couldn't work anyhow because function checking for the
current exception didn't necessarily use the same "global" variable
where it was stored. More formally, old version resulted in ODR
violations and undefined behaviour.

The way we avoid it now is rather ugly and consists in excluding
SWIG_CException from wrapping using the hack in the source code which
postpones wrapping this class until the very end and checks if we had
encountered any %import directives and simply doesn't wrap it if we did.

The same code is used to define the special SWIG_CException_DEFINED
preprocessor symbol which is then used in the generated code to prevent
the SWIG_CException class declaration from being compiled as part of the
wrapper too (because this still happens due to %inline being used for
its definition, and there doesn't seem to be any better way to avoid
this).

This is definitely not pretty, but at least adding "throw(char*)" to a
couple of functions in mod_[ab].i test suite files works now instead of
failing (even without linking and running) as before. This commit
doesn't modify the test suite to avoid possible problems with the other
languages, however.
This commit is contained in:
Vadim Zeitlin 2021-11-25 21:14:56 +01:00
commit 727a65c0e8
2 changed files with 50 additions and 2 deletions
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10
Lib/c/cexcept.swg
View file

@ -11,7 +11,14 @@
extern "C" void SWIG_CException_Raise(int code, const char* msg);
%}
// This class is special too because its name is used in c.cxx source. It is
// only defined if the code there didn't predefine SWIG_CException_DEFINED
// because the class is already defined in another module.
//
// It has to be seen by SWIG because we want to generate wrappers for its
// public functions to be able to use it from the application code.
%inline %{
#ifndef SWIG_CException_DEFINED
class SWIG_CException {
public:
SWIG_CException(const SWIG_CException& ex) throw() : code(ex.code), msg(strdup(ex.msg)) { }
@ -40,16 +47,19 @@ private:
SWIG_CException& operator=(const SWIG_CException& ex);
};
#endif // SWIG_CException_DEFINED
%}
// This part is implementation only and doesn't need to be seen by SWIG.
%{
#ifndef SWIG_CException_DEFINED
SWIG_CException *SWIG_CException::PendingException = 0;
SWIGEXPORTC void SWIG_CException_Raise(int code, const char* msg) {
delete SWIG_CException::PendingException;
SWIG_CException::PendingException = new SWIG_CException(code, msg);
}
#endif // SWIG_CException_DEFINED
%}
%insert("runtime") "swigerrors.swg"