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
getStackPointer()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
noteBottomOfStack()40 void clang::noteBottomOfStack() {
41 if (!BottomOfStack)
42 BottomOfStack = getStackPointer();
43 }
44
isStackNearlyExhausted()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
runWithSufficientStackSpaceSlow(llvm::function_ref<void ()> Diag,llvm::function_ref<void ()> Fn)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