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
21static LLVM_THREAD_LOCAL void *BottomOfStack = nullptr;
22
23static 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
40void clang::noteBottomOfStack() {
41 if (!BottomOfStack)
42 BottomOfStack = getStackPointer();
43}
44
45bool 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(i: 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
66void 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 }, RequestedStackSize: DesiredStackSize);
74}
75

source code of clang/lib/Basic/Stack.cpp