diff options
| -rw-r--r-- | configure.ac | 23 | ||||
| -rw-r--r-- | src/memory.cpp | 68 |
2 files changed, 28 insertions, 63 deletions
diff --git a/configure.ac b/configure.ac index c341183..032ab10 100644 --- a/configure.ac +++ b/configure.ac @@ -181,29 +181,6 @@ esac AC_CHECK_HEADERS([malloc.h malloc_np.h]) AC_CHECK_FUNCS([malloc_trim malloc_usable_size]) -# Check whether compiler supports global sized deallocations. -# If yes, this will improve the memory limiting fallback -# implementation. -# Once we can depend on C++14, this check is no longer necessary. -AC_CACHE_CHECK([if C++ compiler supports -fsized-deallocation], - [sciteco_cv_sized_deallocation_result], [ - AC_LANG_PUSH(C++) - OLD_CXXFLAGS="$CXXFLAGS" - CXXFLAGS="$CXXFLAGS -fsized-deallocation" - AC_COMPILE_IFELSE([AC_LANG_PROGRAM( - [[#include <new>]], - [[(::operator delete)(0, 256)]] - )], sciteco_cv_sized_deallocation_result=yes, - sciteco_cv_sized_deallocation_result=no) - CXXFLAGS="$OLD_CXXFLAGS" - AC_LANG_POP(C++) -]) -if [[ x$sciteco_cv_sized_deallocation_result = xyes ]]; then - AC_DEFINE(HAVE_SIZED_DEALLOCATION, 1, - [C++ compiler supports -fsized-deallocation]) - CXXFLAGS="$CXXFLAGS -fsized-deallocation" -fi - # # Config options # diff --git a/src/memory.cpp b/src/memory.cpp index b592d9e..fd7adf7 100644 --- a/src/memory.cpp +++ b/src/memory.cpp @@ -132,6 +132,18 @@ MemoryLimit memlimit; * Even the malloc_usable_size() workaround for old or non-GNU * compilers is still faster than mallctl() on FreeBSD. * This might need to change in the future. + * - Beginning with C++14 (or earlier with -fsized-deallocation), + * it is possible to globally replace sized allocation/deallocation + * functions, which could be used to avoid the malloc_usable_size() + * workaround. Unfortunately, this may not be used for arrays, + * since the compiler may have to call non-sized variants if the + * original allocation size is unknown - and there is no way to detect + * that when the new[] call is made. + * What's worse is that at least G++ STL is broken seriously and + * some versions will call the non-sized delete() even when sized-deallocation + * is available. Again, this cannot be detected at new() time. + * Therefore, I had to remove the sized-deallocation based + * optimization. */ #ifdef G_OS_WIN32 @@ -179,12 +191,19 @@ MemoryLimit::get_usage(void) * Unfortunately, in the worst case, this will only measure the heap used * by C++ objects in SciTECO's sources; not even Scintilla, nor all * g_malloc() calls. - * Usually, we will be able to use global sized deallocators or + * Usually, we will be able to use global non-sized deallocators with * libc-specific support to get more accurate results, though. */ #define MEMORY_USAGE_FALLBACK +/** + * Current memory usage in bytes. + * + * @bug This only works in single-threaded applications. + * Should SciTECO or Scintilla ever use multiple threads, + * it will be necessary to use atomic operations. + */ static gsize memory_usage = 0; gsize @@ -234,7 +253,9 @@ MemoryLimit::check(void) * The object-specific sized deallocators allow memory * counting portably, even in strict C++11 mode. * Once we depend on C++14, they and the entire `Object` - * class hack can be avoided. + * class hack may be avoided. + * But see above - due to broken STLs, this may not actually + * be safe! */ void * @@ -290,50 +311,19 @@ Object::operator delete(void *ptr, size_t size) noexcept } /* namespace SciTECO */ -#ifdef HAVE_SIZED_DEALLOCATION -/* - * Global sized deallocators must be defined in the - * root namespace. - * Since we only depend on C++11, we cannot just always - * define them (they are a C++14 feature). - * They will effectively measure all C++ allocations, - * including the ones in Scintilla which can make a huge - * difference. - * Due to the poor platform support for memory measurement, - * it's still worth to support them optionally. - */ - -void * -operator new(size_t size) -{ - return SciTECO::Object::operator new(size); -} - -void -operator delete(void *ptr, size_t size) noexcept -{ - SciTECO::Object::operator delete(ptr, size); -} - -/* - * FIXME: I'm a bit puzzled of why this is necessary. - * Apparently, G++ sometimes calls the non-sized, - * FOLLOWED BY the sized deallocator even when - * building Scintilla with -fsized-deallocation. - * It is still uncertain whether the compiler may - * call the non-sized WITHOUT the sized variant. - */ -void operator delete(void *ptr) noexcept {} - -#else /* * In strict C++11, we can still use global non-sized * deallocators. + * * On their own, they bring little benefit, but with * some libc-specific functionality, they can be used * to improve the fallback memory measurements to include * all allocations (including Scintilla). * This comes with a moderate runtime penalty. + * + * Unfortunately, even in C++14, defining replacement + * sized deallocators may be very dangerous, so this + * seems to be as best as we can get (see above). */ void * @@ -358,5 +348,3 @@ operator delete(void *ptr) noexcept #endif g_free(ptr); } - -#endif /* !HAVE_SIZED_DEALLOCATION */ |