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[lua] Run destructors of local C++ objects on SWIG_fail

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Arrange that destructors of local C++ objects in the wrapper function
get run on SWIG_fail (which calls lua_error() which calls longjmp()).

We achieve this by putting almost everything in the function in its
own block, and end that right before lua_error() at which point those
destructors will get called.
This commit is contained in:
Olly Betts 2022-10-13 18:27:48 +13:00 • committed by Olly Betts
commit 9ab9c71623
4 changed files with 58 additions and 4 deletions
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16
Source/Modules/lua.cxx
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@ -556,6 +556,12 @@ public:
this line adds this into the wrapper code
NEW LANGUAGE NOTE:END *********************************************** */
Printv(f->def, "static int ", wname, "(lua_State* L) {", NIL);
// SWIG_fail in lua leads to a call to lua_error() which calls longjmp()
// which means the destructors of any live function-local C++ objects won't
// get run. To avoid this happening, we wrap almost everything in the
// function in a block, and end that right before lua_error() at which
// point those destructors will get called.
if (CPlusPlus) Append(f->def, "\n{");
/* NEW LANGUAGE NOTE:***********************************************
this prints the list of args, eg for a C fn
@ -766,10 +772,12 @@ public:
/* Close the function */
Printv(f->code, "return SWIG_arg;\n", NIL);
// add the failure cleanup code:
Printv(f->code, "\nif(0) SWIG_fail;\n", NIL);
Printv(f->code, "\nfail:\n", NIL);
Printv(f->code, "$cleanup", "lua_error(L);\n", NIL);
Printv(f->code, "return SWIG_arg;\n", NIL);
Printv(f->code, "\nfail: SWIGUNUSED;\n", "$cleanup", NIL);
if (CPlusPlus) Append(f->code, "}\n");
Printv(f->code, "lua_error(L);\n", NIL);
// lua_error() calls longjmp() but we need a dummy return to avoid compiler
// warnings.
Printv(f->code, "return 0;\n", NIL);
Printf(f->code, "}\n");
/* Substitute the cleanup code */