karl3＠writeme.com wrote:
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 Copy Edit 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 Copy Edit 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 Copy Edit 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 Copy Edit 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 Copy Edit 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 Copy Edit sudo apt reinstall g++ libstdc++6 Or force a fresh install:
sh Copy Edit 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 Copy Edit ldd /usr/bin/g++ | grep stdc++ or running your compiled binary with:
sh Copy Edit 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 Copy Edit 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 Copy Edit 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 Copy Edit 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 Copy Edit g++ -print-file-name=libstdc++.so.6 Then try:
sh Copy Edit 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 Copy Edit 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 Copy Edit (long int)a[&c] Which is then attempting: cpp Copy Edit 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 Copy Edit (bool)Test()["hi"] Which then gets converted to long int, and results in: cpp Copy Edit 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 Copy Edit 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 Copy Edit 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 Copy Edit *(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 Copy Edit (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 Copy Edit array[index] == index[array] This is because array subscripting follows the rule:
cpp Copy Edit a[b] == *(a + b) which is commutative when a is a pointer:
cpp Copy Edit b[a] == *(b + a) Does Clang++ Allow This? Yes! Clang also supports index[array], since it's standard C++ behavior. Try this:
cpp Copy Edit #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 Copy Edit 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. === [mistake]
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 ...