> GCC is built with -fno-exceptions. I assume that's mainly to avoid > having to catch and handle exceptions in what was originally C code. > I also assume that also means that there's a policy or convention in > place against throwing exceptions in GCC or making use of constructs > that might throw (such as the non-placement new expressions). It also drops the need of _runtime type info_ (a.k.a. RTTI) and stack unwind table, reducing the size of binary files.
> > By coincidence, bootstrapping my patch for bugs 77531 and 78284 > exposed a few uses of the non-placement array new expression in > dominance.c (in dom_info::dom_init) that may throw an exception(*). > > I'm wondering if those calls should be changed to avoid exceptions. If a program is compiled with `-fno-exceptions` and an exception will have been thrown otherwise, `std::abort()` (or an equivalent such as `__builtin_trap()`) is called. This preserves the semantical correctness of not checking the value of a throwing new expression, since it can't return a null pointer. > > I'm also curious if there really is a policy/convention for dealing > with exceptions in GCC, what it actually is/says. Compilers aren't envisioned to be long-running programs, so aborting on unexpected conditions is reasonable. This isn't only the case for GCC, but also LLVM. > > Thanks > Martin > > [*] My patch exposed these because when -fno-exceptions is used > (and coincidentally also in C++ 98 mode) GCC emits conditional calls > to operator new[](SIZE_MAX) when the size computation that multiplies > the number of elements by the element size exceeds SIZE_MAX. The > -Walloc-size-larger-than warning flags for attempting to allocate > more storage than the size of the biggest object, or SIZE_MAX / 2. ------------------ Best regards, lh_mouse 2016-11-17
