Jeff, David, do you need any more input from my side? -- Marc
Am Sa., 8. Jan. 2022 um 17:32 Uhr schrieb Jeff Law <jeffreya...@gmail.com>: > > > > On 1/6/2022 6:53 AM, David Malcolm via Gcc-patches wrote: > > On Sun, 2021-12-19 at 22:30 +0100, Marc Nieper-Wißkirchen wrote: > >> This patch fixes a memory leak in the pass manager. In the existing > >> code, > >> the m_name_to_pass_map is allocated in > >> pass_manager::register_pass_name, but > >> never deallocated. This is fixed by adding a deletion in > >> pass_manager::~pass_manager. Moreover the string keys in > >> m_name_to_pass_map are > >> all dynamically allocated. To free them, this patch adds a new hash > >> trait for > >> string hashes that are to be freed when the corresponding hash entry > >> is removed. > >> > >> This fix is particularly relevant for using GCC as a library through > >> libgccjit. > >> The memory leak also occurs when libgccjit is instructed to use an > >> external > >> driver. > >> > >> Before the patch, compiling the hello world example of libgccjit with > >> the external driver under Valgrind shows a loss of 12,611 (48 direct) > >> bytes. After the patch, no memory leaks are reported anymore. > >> (Memory leaks occurring when using the internal driver are mostly in > >> the driver code in gcc/gcc.c and have to be fixed separately.) > >> > >> The patch has been tested by fully bootstrapping the compiler with > >> the > >> frontends C, C++, Fortran, LTO, ObjC, JIT and running the test suite > >> under a x86_64-pc-linux-gnu host. > > Thanks for the patch. > > > > It looks correct to me, given that pass_manager::register_pass_name > > does an xstrdup and puts the result in the map. > > > > That said: > > - I'm not officially a reviewer for this part of gcc (though I probably > > touched this code last) > > - is it cleaner to instead change m_name_to_pass_map's key type from > > const char * to char *, to convey that the map "owns" the name? That > > way we probably wouldn't need struct typed_const_free_remove, and (I > > hope) works better with the type system. > > > > Dave > > > >> gcc/ChangeLog: > >> > >> PR jit/63854 > >> * hash-traits.h (struct typed_const_free_remove): New. > >> (struct free_string_hash): New. > >> * pass_manager.h: Use free_string_hash. > >> * passes.c (pass_manager::register_pass_name): Use > >> free_string_hash. > >> (pass_manager::~pass_manager): Delete allocated > >> m_name_to_pass_map. > My concern (and what I hadn't had time to dig into) was we initially > used nofree_string_hash -- I wanted to make sure there wasn't any path > where the name came from the stack (can't be free'd), was saved > elsewhere (danging pointer) and the like. ie, why were we using > nofree_string_hash to begin with? I've never really mucked around with > these bits, so the analysis side kept falling off the daily todo list. > > If/once you're comfortable with the patch David, then go ahead and apply > it on Marc's behalf. > > jeff >
