101–110 of 199 posts
Not a big fan of the format of the talk. The guy is a good orator, but it takes ages to go to the point. A bit annoying if you're actually interested in the technical part rather than the jokes.
This statement would be technically legal on its own in x86 real mode if the compiler didn't do null pointer checks. However it would set the divide-by-zero IRQ handler to itself 0000:0000, and when the next division by zero happened, the machine run into UB (likely a reset or halt) because it would jump there, do 4x ADD byte ptr [BX + SI], AL (or ADD byte ptr [EAX], AL) followed by running the remaining interrupt ve…
If I'm understanding what you're saying correctly, the memory location with address 0 is actually a writable address, but with the value being used semantically to handle division by zero? It's kind of wild to me that would even something that's even allowed to be done manually, let alone required by a certain mode. Is this something provided for compatibility reasons that you'd have to opt into, or is it just someth…
As for why it's address 0, well, it has to go somewhere, every machine has a CPU so everyone needs an interrupt table even if they don't have much memory. And when memory was precious there was no sense wasting even one byte of it; 0 was a real address on your physical memory chip, so why not use it just like any other?
(The fact that it's "address 0" for "division by 0" is just coincidence as far as I can see; division by 0 just happens to be the first kind of possible CPU interrupt. Perhaps it was the most common one?)
Earlier quoted context omitted.
I think a more accurate analogy would be some kind of scalpel that would not let the surgeon cut deeper than they needed. So if they needed a 1 cm incision, it would somehow stop the blade form going in 1.1 cm. In that case, some experienced surgeon may say "But I know how to make a 1cm incision!", but I think that the reality is that preventing a mistake from happening is valuable. You see the same arguments against…
I think an even more accurate analogy would be if a surgeon had some kind of scalpel with a 1 cm limit, but if a surgery suddenly changes in the middle, and suddenly requires a deeper incision, the surgeon has to spend a non-zero amount of time re-configuring the scalpel. This casts flexibility vs safety as a tradeoff, which it is.
Surgeons are constantly killing people[1], and every time, it turns out it was because the surgeon disabled a known, recommended safety rail, and whenever anyone points out that they should stop disabling the safety rails, they insist that they know how to operate without them, it's those other people that don't. Plus it's sooooo inconvenient for an operation[2] to take five more minutes, they're too good to have to deal with that.
[1] introducing security vulnerabilities
[2] code changeset submission
What's passed in there? Some googling let me know it's used on macOS, but every result was too generic to be helpful.
Earlier quoted context omitted.
> sizeof char is 1 by definition everywhere. Parentheses are required around char because it's a type. /pedantic
That is incorrect :-). sizeof is an operator in C, and does not need parenthesis any more than pointer operator *. It is true that programmers frequently think of it as a function and use parenthesis.
To begin with, sizeof has two syntaxes: the first, which is the one you seem to refer to, is simply
sizeof expression
sizeof (type)
Then, even in the first syntax, even if sizeof is listed among the operators, even if it doesn't look any different from "pointer operator ", nonetheless it has strange priority rules. For example
sizeof (T) *x
Not a big fan of the format of the talk. The guy is a good orator, but it takes ages to go to the point. A bit annoying if you're actually interested in the technical part rather than the jokes.
If you use GPT-4 with Browsing turned on and supply it with the title, it will find the page and use the transcript and you can ask it questions. Then you can look at the transcripts to find the spots and verify. Alternatively, if you have an AI-enabled browser you can ask it about the transcript once you open it.
do you mean the browsing plugin, or using base GPT-4?
Earlier quoted context omitted.
Char can be the same size as short or int. You can't assume it is one byte.
You can't assume char is one octet . It is one byte by definition. A byte is CHAR_BIT bits, where CHAR_BIT >= 8. (It's exactly 8 on most implementations; DSPs are the most common exception). short and int are both required to be at least 16 bits wide. It's possible for int to be 1 byte (sizeof (int) == 1), but only if CHAR_BIT >= 16.
If I'm being pedantic, I might add something like
#if CHAR_BIT != 8
#error "This code assumes 8-bit char"
#endif