1 //===--- Stack.cpp - Utilities for dealing with stack space ---------------===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 /// 9 /// \file 10 /// Defines utilities for dealing with stack allocation and stack space. 11 /// 12 //===----------------------------------------------------------------------===// 13 14 #include "clang/Basic/Stack.h" 15 #include "llvm/Support/CrashRecoveryContext.h" 16 17 #ifdef _MSC_VER 18 #include <intrin.h> // for _AddressOfReturnAddress 19 #endif 20 21 static LLVM_THREAD_LOCAL void *BottomOfStack = nullptr; 22 23 static void *getStackPointer() { 24 #if __GNUC__ || __has_builtin(__builtin_frame_address) 25 return __builtin_frame_address(0); 26 #elif defined(_MSC_VER) 27 return _AddressOfReturnAddress(); 28 #else 29 char CharOnStack = 0; 30 // The volatile store here is intended to escape the local variable, to 31 // prevent the compiler from optimizing CharOnStack into anything other 32 // than a char on the stack. 33 // 34 // Tested on: MSVC 2015 - 2019, GCC 4.9 - 9, Clang 3.2 - 9, ICC 13 - 19. 35 char *volatile Ptr = &CharOnStack; 36 return Ptr; 37 #endif 38 } 39 40 void clang::noteBottomOfStack() { 41 if (!BottomOfStack) 42 BottomOfStack = getStackPointer(); 43 } 44 45 bool clang::isStackNearlyExhausted() { 46 // We consider 256 KiB to be sufficient for any code that runs between checks 47 // for stack size. 48 constexpr size_t SufficientStack = 256 << 10; 49 50 // If we don't know where the bottom of the stack is, hope for the best. 51 if (!BottomOfStack) 52 return false; 53 54 intptr_t StackDiff = (intptr_t)getStackPointer() - (intptr_t)BottomOfStack; 55 size_t StackUsage = (size_t)std::abs(StackDiff); 56 57 // If the stack pointer has a surprising value, we do not understand this 58 // stack usage scheme. (Perhaps the target allocates new stack regions on 59 // demand for us.) Don't try to guess what's going on. 60 if (StackUsage > DesiredStackSize) 61 return false; 62 63 return StackUsage >= DesiredStackSize - SufficientStack; 64 } 65 66 void clang::runWithSufficientStackSpaceSlow(llvm::function_ref<void()> Diag, 67 llvm::function_ref<void()> Fn) { 68 llvm::CrashRecoveryContext CRC; 69 CRC.RunSafelyOnThread([&] { 70 noteBottomOfStack(); 71 Diag(); 72 Fn(); 73 }, DesiredStackSize); 74 } 75