=?utf-8?q?José?= L. Junior <[email protected]>,taalhaataahir0102
<[email protected]>,taalhaataahir0102
<[email protected]>,taalhaataahir0102
<[email protected]>,taalhaataahir0102 <[email protected]>,
=?utf-8?q?José?= L. Junior <[email protected]>,
=?utf-8?q?José?= L. Junior <[email protected]>,
=?utf-8?q?José?= L. Junior <[email protected]>,
=?utf-8?q?José?= L. Junior <[email protected]>
Message-ID:
In-Reply-To: <llvm.org/llvm/llvm-project/pull/[email protected]>
================
@@ -246,8 +246,8 @@ class Address {
/// \see Address::DumpStyle
bool Dump(Stream *s, ExecutionContextScope *exe_scope, DumpStyle style,
DumpStyle fallback_style = DumpStyleInvalid,
- uint32_t addr_byte_size = UINT32_MAX,
- bool all_ranges = false) const;
+ uint32_t addr_byte_size = UINT32_MAX, bool all_ranges = false,
+ const char *pattern = nullptr) const;
----------------
taalhaataahir0102 wrote:
Hi @DavidSpickett! Sorry for the delay 🙏
`test_func3(strm, std::move(regex2))` works but it gives the following problem.
When we use `std::move(regex2)` to pass it to `test_func3`, it's essentially
moved, and after the move, the `regex2` in `LookupSymbolInModule` becomes
garbage.
So in functions where pattern is moved multiple times like this:
```
static void DumpAddress(ExecutionContextScope *exe_scope,
const Address &so_addr, bool verbose, bool all_ranges,
Stream &strm, std::optional<llvm::Regex> pattern =
std::nullopt) {
...
...
so_addr.Dump(&strm, exe_scope, Address::DumpStyleResolvedDescription,
Address::DumpStyleInvalid, UINT32_MAX, false,
std::move(pattern));
...
...
if (verbose) {
strm.EOL();
so_addr.Dump(&strm, exe_scope, Address::DumpStyleDetailedSymbolContext,
Address::DumpStyleInvalid, UINT32_MAX, all_ranges,
std::move(pattern));
}
...
}
```
The second `std::move(pattern)`, does not move the original pattern value but
some garbage value. The only way is to make a copy of the original pattern and
then use it with `std::move(copy_pattern)` every time (which doesn't look okay
:-/).
This is the example code and output if I couldn't explain it properly above:
CODE:
```
static void test_func3(Stream &strm, const std::optional<llvm::Regex> pattern =
std::nullopt) {
if (pattern.has_value() && pattern.value().match("main")) {
strm.Printf("Pattern matches 'main' inside test_func3\n");
}
}
static uint32_t LookupSymbolInModule(CommandInterpreter &interpreter,
Stream &strm, Module *module,
const char *name, bool name_is_regex,
bool verbose, bool all_ranges) {
// test_func1(strm, std::make_optional<llvm::Regex>(name));
std::optional<llvm::Regex> regex2 = std::make_optional<llvm::Regex>(name);
if (regex2.has_value()) {
strm.Printf("Pattern has a value\n");
if(regex2.value().match("main")) {
strm.Printf("Pattern matches main\n");
}
else{
strm.Printf("Pattern doesn't match main\n");
}
} else {
strm.Printf("Pattern doesn't have a value\n");
}
test_func3(strm, std::move(regex2));
if (regex2.has_value()) {
strm.Printf("Pattern has a value\n");
if(regex2.value().match("main")) {
strm.Printf("Pattern matches main\n");
}
else{
strm.Printf("Pattern doesn't match main\n");
}
} else {
strm.Printf("Pattern doesn't have a value\n");
} ...
...
}
```
OUTPUT:
```
talha@talha-ROG-Strix-G513QE-G513QE:~/Desktop/LLDB/build/bin$ ./lldb a.out
(lldb) target create "a.out"
Current executable set to '/home/talha/Desktop/LLDB/build/bin/a.out' (x86_64).
(lldb) image lookup -r -s main
Pattern has a value
Pattern matches main
Pattern matches 'main' inside test_func3
Pattern has a value
Pattern doesn't match main
...
...
```
So after `std::move(pattern)`, `pattern != "main"` within the same function
Similarly passing `std::make_optional<llvm::Regex>(name)` to func3 also causes
problem problem:
i.e., `test_func3(strm, std::make_optional<llvm::Regex>(name));`
When we directly pass `std::make_optional<llvm::Regex>(name)`, it creates a
temporary `std::optional<llvm::Regex>` object that is passed directly to
`test_func3`. This temporary object can be moved without requiring an explicit
`std::move` because I guess temporaries are considered rvalues, and
`std::optional` has appropriate move constructors to handle them.
But storing the result of `std::make_optional<llvm::Regex>(name)` in a variable
and then passing it without using `std::move`, if the variable is passed as an
argument to the function, it attempts to perform a copy unless we use
`std::move`. So, initially we can pass it directly to the next dumping function
but further passing it will require `std::move` and the same problem comes
back.
Also 1 last thing for clarification, as discussed later i.e.,
> I think we may be able to reduce the boilerplate by putting the
> prefix/suffix/pattern in a struct, and passing that as an optional assuming
> we can figure out the move issue with regex. But this is for a future change
> if at all.
The struct will be optional and not the member variables inside it as we can
check them in the very first function right?
So the struct will look like:
```
struct information {
pattern, prefix, sufix
}
```
And information will be passed as optional argument rather than
```
struct information {
optional pattern = EMPTY, optional prefix= EMPTY, optional sufix = EMPTY
}
```
https://github.com/llvm/llvm-project/pull/69422
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