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Cast to unsigned char to avoid UB (#152360)

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The standard requires that the argument to functions like `isdigit`, `isalpha`, and similar must be either `EOF` or an `unsigned char`; otherwise, the behavior is undefined (UB).
To avoid out-of-bounds reads, modern implementations of some libraries (such as glibc) deliberately pad their internal tables to guarantee valid memory access even for negative values. However, this is implementation-specific, and other libraries may not do this.

Properly casting the argument to `unsigned char` is good practice to avoid potential issues on some platforms.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/152360
Approved by: https://github.com/cyyever, https://github.com/Skylion007
This commit is contained in:
io-no
2025-04-30 15:09:10 +00:00
committed by PyTorch MergeBot
parent 4408701fed
commit d88e0ceb64
2 changed files with 7 additions and 5 deletions
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5
aten/src/ATen/core/Dimname.cpp
View File

@ -25,9 +25,10 @@ bool Dimname::isValidName(const std::string& name) {
}
for (auto it = name.begin(); it != name.end(); ++it) {
// NOLINTNEXTLINE(bugprone-branch-clone)
if (std::isalpha(*it) || *it == '_') {
const unsigned char ch = static_cast<unsigned char>(*it);
if (std::isalpha(ch) || ch == '_') {
continue;
} else if (it != name.begin() && std::isdigit(*it)) {
} else if (it != name.begin() && std::isdigit(ch)) {
continue;
}
return false;

7
c10/core/Device.cpp
View File

@ -83,10 +83,11 @@ Device::Device(const std::string& device_string) : Device(Type::CPU) {
pstate != DeviceStringParsingState::ERROR && i < device_string.size();
++i) {
const char ch = device_string.at(i);
const unsigned char uch = static_cast<unsigned char>(ch);
switch (pstate) {
case DeviceStringParsingState::START:
if (ch != ':') {
if (isalpha(ch) || ch == '_') {
if (std::isalpha(uch) || ch == '_') {
device_name.push_back(ch);
} else {
pstate = DeviceStringParsingState::ERROR;
@ -97,7 +98,7 @@ Device::Device(const std::string& device_string) : Device(Type::CPU) {
break;
case DeviceStringParsingState::INDEX_START:
if (isdigit(ch)) {
if (std::isdigit(uch)) {
device_index_str.push_back(ch);
pstate = DeviceStringParsingState::INDEX_REST;
} else {
@ -110,7 +111,7 @@ Device::Device(const std::string& device_string) : Device(Type::CPU) {
pstate = DeviceStringParsingState::ERROR;
break;
}
if (isdigit(ch)) {
if (std::isdigit(uch)) {
device_index_str.push_back(ch);
} else {
pstate = DeviceStringParsingState::ERROR;