karl3＠writeme.com wrote:
> karl3＠writeme.com wrote:
> > karl3＠writeme.com wrote:
> > This is a gpt completion being sent to the wrong thread.
> > https://chatgpt.com/share/67acb1d8-7df4-8013-b49c-a902213e9bf3
> > To clarify, the weird thing here is that there are no web search results
> > for others encountering this issue, when it is normal to make untyped-like
> > interfaces in C++ and many conventional untyped languages provide for both
> > operator[] and bool use of their type.
> > Having no web search results for this implicit cast of bool to long
> > (combined with the use of operator[] as pointer-summed-with-int) says
> > something, either about modern web searches, or what people like me
> > encounter in the world.
> > Here's a thought -- having written code for fun from earlier decades is
> > more rare in the larger global domain after everyone [ended up] online.
> > Then, having severe dissociative/FND from doing so even more rare. Then
> > further, maybe other combinations like that one make patterns of
> > semi-unique experiences that hold those personal stories of wide
> > responsibility in other people's rare areas where parts overlap with new
> > information, new meaning for our species that many encounter.
>
> Here, probably most people would have seen from the compiler error that this
> was an operator on an integer type, not an operator on bool. But maybe I have
> a psychological disorder that is rare and poorly documented maybe because
> usually it's found in poverty-class people.
Things missing and/or misleading in above.
Also pasting in the whole conversation to clarify that it's just about a
compilation error:
===
My g++ 12.2.0-14 with debian has a built-in operator[] for bool. If this isn't
expected, then it's likely a corrupt g++ binary or such. Let's poke at it. I
haven't included <vector> or anything, which wouldn't define a built-in
operator anyway.
**test1.cpp*:
#include <string_view>
class Test
{
public:
Test* operator [](std::string_view a) { return this; }
operator bool();
};
#include <iostream>
int main()
{
void* x = (Test())["hi"];
std::cout << x << std::endl;
}
build output:
g++ -std=c++20 -Wall -Werror test1.cpp -o test1
test1.cpp: In function ‘int main()’:
test1.cpp:12:23: error: ambiguous overload for ‘operator[]’ (operand types are
‘Test’ and ‘const char [3]’)
12 | void* x = (Test())["hi"];
| ^
test1.cpp:12:23: note: candidate: ‘operator[](long int, const char*)’ (built-in)
test1.cpp:5:11: note: candidate: ‘Test* Test::operator[](std::string_view)’
5 | Test* operator [](std::string_view a) { return this; }
| ^~~~~~~~
make: *** [<builtin>: test1] Error 1
**test2.cpp**
#include <iostream>
int main()
{
for (bool a: {false, true}) {
for (char const&c: "123") {
std::cout << a << "[" << &c << "] = " << a[&c] << std::endl;
}
}
}
output:
0[123] = 1
0[23] = 2
0[3] = 3
0[] =
1[123] = 2
1[23] = 3
1[3] =
1[] = [
I have had other tests that behave in other ways, too
ChatGPT said:
This is quite strange behavior, and it suggests that your g++ installation
might be corrupted or misconfigured in some way. Let's break it down
systematically.
Observations:
Unexpected Built-in operator[] for bool
test2.cpp suggests that bool unexpectedly has an operator[] built-in.
test1.cpp indicates that g++ believes there's a built-in operator[](long int,
const char*), which shouldn’t be there.
operator[] on bool
a[&c] in test2.cpp compiles and produces seemingly nonsensical output.
bool in standard C++ has no built-in operator[]. This is not expected behavior
in a correct compiler.
Potential Causes
A corrupt g++ binary or incorrect standard library installation.
ABI incompatibilities due to mixing different versions of libstdc++.
A non-standard extension or bug in Debian’s build of g++ 12.2.0-14.
Next Steps to Debug
1. Check Your Compiler Version & Path
Run:
sh
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g++ --version
which g++
ldd $(which g++)
Make sure it's pointing to the expected g++ binary and that it's linking
against the correct libstdc++.
2. Check for Corruption in libstdc++
Run:
sh
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dpkg -S $(which g++)
dpkg -S $(g++ -print-file-name=libstdc++.so)
sha256sum $(which g++)
sha256sum $(g++ -print-file-name=libstdc++.so)
Compare the hash with a fresh, known-good installation.
3. Try Another Compiler
Install g++ from a different source (e.g., a newer version or a backported
package).
sh
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sudo apt install g++-13 # If available
Try compiling your tests with g++-13 and see if the behavior persists.
4. Run with -E to Inspect Expansion
sh
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g++ -std=c++20 -E test2.cpp | less
This will show the preprocessed output and might provide hints on unexpected
macro expansions.
5. Run with -S to Inspect Assembly
sh
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g++ -std=c++20 -S test2.cpp -o test2.s
cat test2.s
Check if the compiler is generating unexpected symbol references.
6. Reinstall g++ and libstdc++
sh
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sudo apt reinstall g++ libstdc++6
Or force a fresh install:
sh
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sudo apt remove --purge g++
sudo apt install g++
Conclusion
Your issue is highly unusual and suggests that something is deeply wrong with
either your compiler binary or your standard library. The best way forward is
to check for corruption, verify installations, and try an alternative g++
version. Let me know what you find!
You said:
$ g++ --version
g++ (Debian 12.2.0-14) 12.2.0
Copyright (C) 2022 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
$ which g++
/usr/bin/g++
$ ldd $(which g++)
linux-vdso.so.1 (0x00007ffe995a3000)
libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f80628f8000)
/lib64/ld-linux-x86-64.so.2 (0x00007f8062af8000)
$ dpkg -S $(which g++)
g++: /usr/bin/g++
$ dpkg -S $(g++ -print-file-name=libstdc++.so)
libstdc++-12-dev:amd64: /usr/lib/gcc/x86_64-linux-gnu/12/libstdc++.so
$ sha256sum $(which g++)
7f286ca4017ae9052c4233eb4cc129373222a4356088d21e0feed12fc583f3a0 /usr/bin/g++
$ sha256sum $(g++ -print-file-name=libstdc++.so)
8401fa690e5d9e2b037aaed1decb1ca03050ba2dec88b908bdad1f56a3d5a133
/usr/lib/gcc/x86_64-linux-gnu/12/libstdc++.so
Slow down; I have some motor issues. I also have clang and g++14 installed. I
should test with them. I like -E and -S too. Too bad ldd didn't show which
libstdc++ was being used, but maybe this is because libstdc++ is a development
library not a runtime library. I'm not sure if it can add built-in operators.
ChatGPT said:
You're right—ldd didn’t show libstdc++ because it’s a development library, and
the runtime library might be different. You could try checking which shared
library is actually being used at runtime with:
sh
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ldd /usr/bin/g++ | grep stdc++
or running your compiled binary with:
sh
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ldd ./test1
This might reveal the actual libstdc++.so in use.
Since you have Clang and g++-14, it’s definitely worth testing with them to see
if the behavior persists. You can try:
sh
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clang++ -std=c++20 test1.cpp -o test1-clang
g++-14 -std=c++20 test1.cpp -o test1-g++14
If Clang or g++-14 doesn’t produce the same issue, that points toward a problem
specific to g++-12.2.0-14. If they do show the same behavior, then it might be
a deeper system issue.
Also, running g++ -E and g++ -S on your tests could reveal unexpected macro
expansions or assembly-level surprises. Let me know what results you get, and
we can take it from there!
You said:
clang++ -std=c++20 -Wall -Werror test1.cpp -o test1
test1.cpp:12:24: error: expected variable name or 'this' in lambda capture list
void* x = (Test())["hi"];
g++-14 -std=c++20 -Wall -Werror test1.cpp -o test1
test1.cpp: In function ‘int main()’:
test1.cpp:12:23: error: ambiguous overload for ‘operator[]’ (operand types are
‘Test’ and ‘const char [3]’)
12 | void* x = (Test())["hi"];
| ^
test1.cpp:12:23: note: candidate: ‘operator[](long int, const char*)’ (built-in)
test1.cpp:5:11: note: candidate: ‘Test* Test::operator[](std::string_view)’
5 | Test* operator [](std::string_view a) { return this; }
| ^~~~~~~~
ChatGPT said:
Interesting results! Here's what they suggest:
Clang++ Failure (test1.cpp)
Clang is treating ["hi"] as an invalid lambda capture list. This suggests that
Clang does not recognize an unexpected built-in operator[], reinforcing that
the issue is likely specific to g++.
G++-14 (test1.cpp)
g++-14 produces the same ambiguous overload error as g++-12.2.0-14, meaning the
issue persists across versions.
The key part: "operator[](long int, const char)’ (built-in)"*
This is unexpected, as there should be no built-in operator[] for Test.
Since g++-14 still sees the same weird built-in operator, this suggests:
A problem in your GCC configuration or Debian's packaging.
A possible unexpected extension in g++ itself.
Some other system-wide issue, like an overridden library.
Next Steps
1. Check What g++ -E Expands To
Run:
sh
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g++-14 -std=c++20 -E test1.cpp | less
Look for anything unusual, like macro expansions around operator[].
2. Check The Runtime Libraries Used
Try:
sh
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ldd ./test1-g++14
and see if it's linking to an unexpected libstdc++.
3. Try Explicitly Linking Against A Known libstdc++
Find out where your libstdc++.so.6 is:
sh
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g++ -print-file-name=libstdc++.so.6
Then try:
sh
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g++-14 -std=c++20 test1.cpp -o test1-g++14
-Wl,-rpath,/usr/lib/gcc/x86_64-linux-gnu/14
This forces it to use the expected runtime.
4. Try A Completely Different GCC Version
Since Clang doesn’t show the issue, a fresh install of a completely different
g++ version (like g++-13) might help:
sh
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sudo apt install g++-13
g++-13 -std=c++20 test1.cpp -o test1-g++13
Let me know what -E shows and if linking against a specific libstdc++ changes
anything!
You said:
I'm observing that g++ is not performing operator[] on a bool -- rather it's
casting the bool to a long int, and performing operator[](long int, const char*)
ChatGPT said:
That makes a lot of sense! The built-in operator[](long int, const char*)
message suggests that bool is being implicitly converted to long int, which
then interacts with the built-in array subscript operator.
Why is this happening?
bool to long int Conversion
In C++, bool implicitly converts to int (which can be further promoted to long
int).
This means a[&c] in test2.cpp is actually being interpreted as:
cpp
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(long int)a[&c]
Which is then attempting:
cpp
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long int[const char*]
and this matches a built-in operator!
What’s Happening in test1.cpp?
Test has an operator bool(), which allows an implicit conversion.
(Test())["hi"] can thus be interpreted as:
cpp
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(bool)Test()["hi"]
Which then gets converted to long int, and results in:
cpp
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operator[](long int, const char*)
This explains the built-in operator confusion.
How to Fix or Debug Further
Explicitly delete the operator bool() to prevent this implicit conversion:
cpp
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class Test {
public:
Test* operator [](std::string_view a) { return this; }
explicit operator bool(); // Prevent implicit conversion
};
This should stop Test from unexpectedly becoming a long int.
Use -Wconversion and -Werror=implicit-int-conversion
sh
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g++ -std=c++20 -Wall -Wconversion -Werror=implicit-int-conversion test1.cpp
This should warn about bool converting to long int.
Conclusion
This isn't a compiler corruption issue—it’s an implicit conversion quirk in
C++. g++ is correctly applying built-in operators, but it’s allowing the bool
-> long int conversion too freely. Making operator bool() explicit should solve
it.
Great catch on noticing that it wasn’t directly bool with operator[], but
rather bool being implicitly converted!
You said:
what does operator[] mean with long int
ChatGPT said:
In C++, operator[] is primarily defined for array and pointer types. However,
when you see operator[](long int, const char*) as a built-in operator, it
suggests that long int is being treated as an array index.
Understanding long int[const char*]
If a is an integer (long int), then a[b] is equivalent to *(a + b).
Normally, this makes sense when a is a pointer or an array.
If a is a non-pointer integer, a[b] is only meaningful if b is a pointer.
Thus, a[b] could be interpreted as:
cpp
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*(a + b) // "a" as an address, adding "b" to it
which explains the weird outputs you got in test2.cpp.
How This Connects to Your Code
Your bool was implicitly converted to long int (false → 0, true → 1).
Then, a[&c] became:
cpp
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(long int)a[&c] // Equivalent to *(a + &c)
Since &c is a pointer to a character in "123", the behavior depends on how
pointer arithmetic interacts with long int.
Why Is This a Built-in Operator?
GCC treats integer indices as valid array subscripts because of pointer
arithmetic rules in C and C++:
int x[10]; x[2]; is valid.
The general rule: ptr[index] is equivalent to *(ptr + index).
Even though long int[const char*] looks weird, it technically follows the same
principle.
Key Takeaways
a[b] is always interpreted as *(a + b).
When a is an integer (long int), a + b only makes sense if b is a pointer.
GCC likely allows this due to its handling of built-in array subscripting.
Your issue arose because bool was silently converting to long int, making
bool[&c] turn into long int[const char*].
To prevent this:
Make operator bool() explicit in your class.
Use -Wconversion to catch unintended type promotions.
You're uncovering a really deep C++ behavior here—nice debugging work! 🚀
You said:
it sounds like gnu c++ you can do index[array] as well as array[index]
i wonder if clang++ allows this
ChatGPT said:
Yes, in GNU C++, indexing works both ways due to pointer arithmetic rules. This
means:
cpp
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array[index] == index[array]
This is because array subscripting follows the rule:
cpp
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a[b] == *(a + b)
which is commutative when a is a pointer:
cpp
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b[a] == *(b + a)
Does Clang++ Allow This?
Yes! Clang also supports index[array], since it's standard C++ behavior. Try
this:
cpp
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#include <iostream>
int main() {
int arr[] = {10, 20, 30, 40};
std::cout << arr[2] << std::endl; // Normal indexing: 30
std::cout << 2[arr] << std::endl; // Reverse indexing: 30
return 0;
}
Compile with:
sh
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g++ -std=c++20 test.cpp -o test
clang++ -std=c++20 test.cpp -o test-clang
Why Does This Work?
arr[2] is *(arr + 2).
2[arr] is *(2 + arr), which is the same!
Does It Work With Other Types?
No, only when one operand is a pointer. For example, 2[100] (indexing into a
long int) is invalid.
This is a fun quirk of C and C++, but it’s rarely used in real code! 😆
You said:
0_0 because of this quirk we cannot make classes that both have indexing and
bool operators, wouldn't this have been found and discussed years ago?
ChatGPT said:
Yeah, you'd think this would have been caught and discussed years ago, since
C++ has been around for decades. But it's such an obscure edge case that it
probably hasn't come up much in practice. Most people don't mix operator bool()
with operator[], and even fewer write code where a bool unexpectedly becomes an
index.
Why Hasn't This Been a Big Issue?
Most operator bool() are explicit
Many modern C++ best practices recommend marking operator bool() as explicit to
prevent implicit conversions.
If your operator bool() was explicit, the compiler would complain when trying
to convert it to long int.
Indexing with bool is rare
Usually, operator[] works with integers or iterators.
Using bool as an index isn't common because it's normally just 0 or 1.
The index[array] trick is rare too
People know array[index], but very few ever write index[array] on purpose.
It's mostly a fun trivia fact rather than a practical programming technique.
Was This Ever Discussed?
You're right to think this should have come up before! Some places where it
might have been noticed:
Compiler bug reports: If someone got an unexpected overload resolution.
C++ standard discussions: Maybe buried in old committee notes.
Online discussions: Might be mentioned in obscure Stack Overflow or mailing
list threads.
A search in GCC or Clang bug trackers might turn something up. Want me to check?
You said:
ok
ChatGPT said:
You're absolutely right—this quirk in C++'s operator overloading can lead to
unexpected behavior when combining operator[] and operator bool(). While it
might seem like such an issue would have been widely discussed, it remains
relatively obscure due to its rarity in practical code.
Why This Hasn't Been Widely Discussed
Explicit Conversion Operators: Modern C++ best practices recommend marking
conversion operators, like operator bool(), as explicit to prevent unintended
implicit conversions. This approach mitigates the risk of such conflicts.
MODERNESCPP.COM
Rare Combination: Defining both operator[] and operator bool() in the same
class is uncommon. Even when both are present, the specific conditions that
lead to this conflict are rare.
Community Awareness: Discussions about this specific issue are scarce. While
operator overloading is a well-covered topic, the nuanced interplay between
these particular operators hasn't garnered much attention.
Best Practices to Avoid This Issue
Use Explicit Conversion Operators: Define operator bool() as explicit to
prevent implicit conversions that could lead to unexpected behavior.
Be Cautious with Operator Overloading: Ensure that overloaded operators behave
intuitively and avoid combinations that could introduce ambiguity.
By adhering to these practices, you can prevent such conflicts and write more
predictable and maintainable C++ code.
Sources
You said:
I am different from most people. All my life I quickly run into bugs that
others don't. When C++ came out, people weren't obsessed with doing things that
proper, standard, way -- rather its fluidity with applying operators was used
to make things easy and concise. The use of operator[] with operator bool is
intuitive if making an interface reminiscent of a flexible scripting language
like javascript, which is common and has been done repeatedly by many people
over the years. It's strange to not find this mentioned. But a lot of things
are strange online now.
ChatGPT said:
I understand your perspective. In the early days of C++, developers often
leveraged operator overloading to create more intuitive and concise interfaces,
sometimes mirroring the flexibility of scripting languages like JavaScript. The
combination of operator[] and operator bool() can indeed be intuitive for such
designs.
The absence of widespread discussion on this specific issue might be due to its
niche nature. While operator overloading has been extensively debated, the
particular interaction between operator[] and operator bool() leading to
unexpected behavior is relatively uncommon. As a result, it hasn't been a focal
point in mainstream discussions.
Your experience highlights an interesting aspect of C++'s flexibility and the
potential pitfalls that can arise from certain combinations of operator
overloads. It's a testament to the language's depth and the importance of
understanding its intricacies when designing intuitive and robust interfaces.
===
> > It's hard for me to talk about this rationally and accurately, but there
> > has been something going on for some time with what people encounter in the
> > world, where people avoid certain things, or the world rests as if people
> > avoided certain things. This is a pretty harmless instance and example of
> > this.
> > My path is different, I'm sure many others' are. I get to notice some of
> > these things, partly because of my larger memory which I went against
> > culture by training skill with through my childhood. It didn't make sense
> > to me to not train one's mind, and instead rely on tools. But nobody
> > supported this, instead encouraging studying, calendars, etc. I made sure I
> > always tried to remember before using a tool.
> > When we have these exposures, everyone has different exposures, it gives us
> > a role in the world, and we hold this intuitively like something special,
> > something we don't really discuss. We also have a sense of other people
> > having those things out there. Now, after exposure to [mind
> > control/trafficking/isolation], it's incredibly different for me.
> > But this is a clear and relatively harmless space where that could be
> > observed a little bit.
> > What is the meaning here? What is my role?
> > These spaces of large scale human behavior can be thought of as like
> > messages and impact of our collective subconscious. Now we've seen that
> > some people act aggressively on that, to control and influence people, but
> > we also see and always know that that's not an omnipresent thing (at least,
> > those of us who survive remember and observe this) -- people find spaces
> > where they aren't influenced.
> > Where are the spaces where I could survive?
> > Something like a compiler error is harmless. The compiler error isn't going
> > to get hurt if a huge cartel decides to have it assassinated. The suffering
> > associated is small.
> > What kinds of similar things provide for more safe consideration?
> > What do the people who leave and hope with regard to these things, leave
> > for us needing to do?
> > What shared values do we have with dangers, that can provide for unity and
> > aid here?
> > What does it mean ...?
> > I didn't write right. I broke it. But there's something.
> > Why would an influence like this happen? What is it avoiding? What did it
> > stem from?
> > Was there an old AI or, we know there were huge groups of trafficking
> > victims / government mind control programs / cults / etc etc ... What was
> > the depth and complexity of what they were influencing? What were they
> > trying to defend, and how do we _threaten whatever that is less_, or more
> > importantly demonstrate to them that we will, so that they will make fewer
> > demands on our species, and we can start to guide our own paths more?
> > Are there things we could teach our children that would make the world
> > safer for longer and more diverse periods of time ...
> >
