jpenix-quic marked 2 inline comments as done. jpenix-quic added inline comments.
================ Comment at: flang/runtime/environment.cpp:77 +#else + envp = environ; +#endif ---------------- peixin wrote: > What is `environ` used for? Should we try to keep as less extern variable as > possible in runtime for security. I think `setenv` is only required to make sure that the `environ` pointer points to the correct copy of the environment variables. So, as long as we are storing a copy of the environment pointer in `ExecutionEnvironment` and potentially making changes to the environment via `setenv`, I think we need to base it off the `environ` pointer after `setenv` has been called rather than the `envp` from `main`. That said, I don't think the `envp` variable we are storing is being used for anything at the moment (reading environment variables was changed to use `getenv` rather than `envp` in the commit [[ https://github.com/llvm/llvm-project/commit/824bf908194c9267f1f09065ba8e41d7969006ab | here]]). If removing the usage of `environ` is preferable, we could maybe remove the usage of `envp` altogether (in a separate patch)--does this sound like a good idea or would it be better to just leave in the `environ` usage for now? ================ Comment at: flang/test/Driver/emit-mlir.f90:16 ! CHECK-NEXT: } +! CHECK-NEXT: fir.global @_QQEnvironmentDefaults constant : !fir.ref<tuple<i[[int_size:.*]], !fir.ref<!fir.array<0xtuple<!fir.ref<i8>, !fir.ref<i8>>>>>> { +! CHECK-NEXT: %[[VAL_0:.*]] = fir.zero_bits !fir.ref<tuple<i[[int_size]], !fir.ref<!fir.array<0xtuple<!fir.ref<i8>, !fir.ref<i8>>>>>> ---------------- peixin wrote: > jpenix-quic wrote: > > peixin wrote: > > > Is it possible not to generated this global variable if `fconvert=` is > > > not specified? > > I'm not entirely sure--the issue I was running into was how to handle this > > in Fortran_main.c in a way which worked for all of GCC/Clang/Visual Studio > > (and maybe others?). I was originally thinking of doing this by using a > > weak definition of _QQEnvironmentDefaults set to nullptr so fconvert, etc. > > could override this definition without explicitly generating the fallback > > case. For GCC/clang, I think I could use __attribute__((weak)), but I > > wasn't sure how to handle this if someone tried to build with Visual Studio > > (or maybe another toolchain). I saw a few workarounds (ex: > > https://devblogs.microsoft.com/oldnewthing/20200731-00/?p=104024) but I > > shied away from this since it seems to be an undocumented feature (and > > presumably only helps with Visual Studio). > > > > Do you know of a better or more general way I could do this? (Or, is there > > non-weak symbol approach that might be better that I'm missing?) > How about generate one runtime function with the argument of > `EnvironmentDefaultList`? This will avoid this and using one extern variable? > > If users use one variable with bind C name `_QQEnvironmentDefaults` in > fortran or one variable with name `_QQEnvironmentDefaults` in C, it is risky. > Would using the runtime function and static variable with the type > `EnvironmentDefaultList` in runtime be safer? Agreed that there are potential risks with the current approach (although, are the `_Q*` names considered reserved?). Unfortunately, I think generating a call to set the environment defaults requires somewhat significant changes to the runtime. The runtime reads environment variables during initialization in `ExecutionEnvironment::Configure` which is ultimately called from the "hardcoded" `Fortran_main.c` and I need to set the defaults before this happens. So, I believe I'd either have to move the initialization to `_QQmain` or make it so that `main` isn't hardcoded so that I could insert the appropriate runtime function. @klausler I think I asked you about this when I was first trying to figure out how to implement the environment defaults and you suggested I try the extern approach--please let me know if you have thoughts/suggestions around this! CHANGES SINCE LAST ACTION https://reviews.llvm.org/D130513/new/ https://reviews.llvm.org/D130513 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
