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From: Nils-Christian Kempke <nckempke@sourceware.org> To: gdb-cvs@sourceware.org Subject: [binutils-gdb] gdb, testsuite, fortran: fix double free in mixed-lang-stack.exp Date: Tue, 31 May 2022 14:46:19 +0000 (GMT) [thread overview] Message-ID: <20220531144619.527A8395A065@sourceware.org> (raw) https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=a60ead5ded5f9fc548018637d4810cb5f313ad8c commit a60ead5ded5f9fc548018637d4810cb5f313ad8c Author: Nils-Christian Kempke <nils-christian.kempke@intel.com> Date: Tue May 31 16:43:45 2022 +0200 gdb, testsuite, fortran: fix double free in mixed-lang-stack.exp While testing mixed-lang-stack I realized that valgrind actually complained about a double free in the test. All done ==2503051== ==2503051== HEAP SUMMARY: ==2503051== in use at exit: 0 bytes in 0 blocks ==2503051== total heap usage: 26 allocs, 27 frees, 87,343 bytes allocated ==2503051== ==2503051== All heap blocks were freed -- no leaks are possible ==2503051== ==2503051== For lists of detected and suppressed errors, rerun with: -s ==2503051== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 0 from 0) Reason for this is that in mixed-lang-stack.cpp in mixed_func_1f an object "derived_type obj" goes on the stack which is then passed-by-value (so copied) to mixed_func_1g. The default copy-ctor will be called but, since derived_type contains a heap allocated string and the copy constructor is not implemented it will only be able to shallow copy the object. Right after each of the functions the object gets freed - on the other hand the d'tor of derived_type actually is implemented and calls free on the heap allocated string which leads to a double free. Instead of obeying the rule of 3/5 I just got rid of all that since it does not serve the test. The string is now just a const char* = ".." object member. Diff: --- gdb/testsuite/gdb.fortran/mixed-lang-stack.cpp | 12 +----------- 1 file changed, 1 insertion(+), 11 deletions(-) diff --git a/gdb/testsuite/gdb.fortran/mixed-lang-stack.cpp b/gdb/testsuite/gdb.fortran/mixed-lang-stack.cpp index 39ff6c201f7..b5ae7dac0a8 100644 --- a/gdb/testsuite/gdb.fortran/mixed-lang-stack.cpp +++ b/gdb/testsuite/gdb.fortran/mixed-lang-stack.cpp @@ -26,17 +26,7 @@ class base_one class base_two { public: - base_two () - { - string = strdup ("Something in C++"); - } - - ~base_two () - { - free (string); - } - - char *string = nullptr; + const char *string = "Something in C++"; float val = 3.5; };
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