zig / under the hood
DUE 000 DECK 000 STREAK 0d LESSONS 0/14 saved in this browser only
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0x00
How many distinct values can n bits represent?
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Range of u8 and of i8?
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The byte 0xFF read as u8 and as i8?
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How do you negate a two's complement number by hand?
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Why do CPUs use two's complement for signed integers?
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How many bits does one hex digit represent?
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Zero extension vs sign extension?
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In Zig, what happens when a u8 holding 255 gets + 1 at runtime?
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@intCast vs @truncate vs @bitCast?
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Convert 0000_1101 to decimal.
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Convert 200 to binary.
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What is the sign bit?
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Convert 0000_1101 to decimal.
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Convert 200 to binary.
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What is the sign bit?
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0x01
At the machine level, what is a pointer?
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0x01
Bytes of the u32 0x11223344 in memory, lowest address first, on x86-64?
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What is network byte order?
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What does an alignment of N require?
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Size of extern struct { a: u8, b: u32, c: u8 }, and why?
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Why do structs get tail padding?
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Zig struct vs extern struct vs packed struct?
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0x01
Which builtins inspect a type's layout in Zig?
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0x01
What do &x and p.* mean in Zig?
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Why are all pointers on a 64-bit machine the same size?
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0x01
Why can a misaligned value be slow, or crash?
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0x01
What do &x and p.* mean in Zig?
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0x01
Why are all pointers on a 64-bit machine the same size?
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0x01
Why can a misaligned value be slow, or crash?
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0x02
What does the instruction pointer (rip) hold?
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0x02
Describe the CPU's basic cycle.
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0x02
How many general-purpose registers does x86-64 have?
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0x02
What is an ISA?
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0x02
What does the flags register record?
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0x02
What does a branch misprediction cost, and why?
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0x02
What is cmov and why do compilers like it?
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0x02
How can you see the assembly Zig generates?
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0x02
What is assembly?
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0x02
How do if and loops work at the machine level?
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0x02
What is a clock cycle?
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0x02
What is assembly?
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How do if and loops work at the machine level?
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0x02
What is a clock cycle?
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0x03
Which way does the x86-64 stack grow?
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0x03
What exactly do call and ret do?
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0x03
What's in a stack frame?
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0x03
Why is stack allocation nearly free?
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0x03
Why is returning a pointer to a local variable a bug?
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0x03
System V x86-64: which registers carry the first six integer arguments?
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Which registers are callee-saved in System V x86-64?
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0x03
Typical main-thread stack size on Linux?
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Why is the call stack a stack (last in, first out)?
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0x03
What stops a stack overflow from corrupting other memory?
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0x03
Three fixes for returning a pointer to a local variable?
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Why is the call stack a stack (last in, first out)?
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0x03
What stops a stack overflow from corrupting other memory?
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0x03
Three fixes for returning a pointer to a local variable?
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0x04
When must data live on the heap rather than the stack?
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0x04
How does glibc's malloc get memory from the Linux kernel?
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0x04
What is a bump (arena) allocator?
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0x04
What is heap fragmentation?
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0x04
Name the three classic manual memory bugs.
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0x04
Does free usually return memory to the OS?
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0x04
What is a pool allocator good for?
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0x04
What does a garbage collector do that Zig leaves to you?
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0x04
Why don't allocators ask the OS for memory on every small allocation?
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0x04
What does a garbage collector do that Zig leaves to you?
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0x04
Why don't allocators ask the OS for memory on every small allocation?
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0x05
Cache line size on x86-64?
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0x05
Rough latency of an L1 hit vs a trip to RAM?
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0x05
Spatial vs temporal locality?
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0x05
Why is walking a 2D array row by row faster than column by column?
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Why are linked lists cache-unfriendly?
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Array of structs vs struct of arrays, and Zig's tool for the latter?
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What is false sharing?
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0x05
What is a cache hit vs a cache miss?
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0x05
What does the hardware prefetcher do?
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What is a cache hit vs a cache miss?
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0x05
What does the hardware prefetcher do?
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0x06
What does the MMU do?
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0x06
Typical page size on x86-64?
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0x06
What is the TLB?
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0x06
The two outcomes of a page fault?
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0x06
Why does dereferencing null crash reliably?
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0x06
Why can mmap of a huge region return instantly?
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0x06
What are .text, .data and .bss?
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0x06
Where do the heap and stack sit, and which way does each grow?
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0x06
What does virtual memory give you?
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0x06
Which part of a virtual address gets translated?
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0x06
What does virtual memory give you?
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0x06
Which part of a virtual address gets translated?
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0x07
What is a system call?
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0x07
x86-64 Linux: where do the syscall number and result go?
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0x07
Syscall argument registers on x86-64 Linux, and the odd one out?
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0x07
Syscall numbers of write and exit on x86-64 Linux?
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0x07
What are file descriptors 0, 1 and 2?
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Process vs thread?
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Which tool shows a program's syscalls on Linux?
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0x07
Why does switching processes cost more than switching threads?
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0x07
What are user mode and kernel mode?
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0x07
Why do I/O libraries buffer output?
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0x07
What does a shell set up for cat a | grep x?
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0x07
What are user mode and kernel mode?
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0x07
Why do I/O libraries buffer output?
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0x07
What does a shell set up for cat a | grep x?
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0x08
const vs var in Zig?
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0x08
What does undefined mean, and how does Debug mode help?
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0x08
How do you silence an unused local variable error?
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0x08
Which implicit integer conversions does Zig allow?
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0x08
Name the four build modes and which keep safety checks.
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0x08
How does a labeled block return a value?
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0x08
What does "no hidden control flow" mean in Zig?
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0x08
zig run file.zig vs zig test file.zig?
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0x08
What does @import("std") do, and what does the @ mean?
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0x08
Format specifiers {s}, {d} and {x} in std.debug.print?
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0x08
What is p.length() shorthand for, when length is declared in struct Point?
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0x08
What does @import("std") do, and what does the @ mean?
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0x08
Format specifiers {s}, {d} and {x} in std.debug.print?
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0x08
What is p.length() shorthand for, when length is declared in struct Point?
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0x09
*T vs [*]T vs []T?
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0x09
@sizeOf([]u8) on a 64-bit machine?
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0x09
How do you dereference a pointer p in Zig?
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0x09
Type of the string literal "hello"?
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0x09
Which elements does arr[1..3] include?
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0x09
What does [:0]u8 mean?
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0x09
Size of ?*T compared to *T?
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0x09
Out-of-bounds slice index in Debug vs ReleaseFast?
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0x09
How do you compare two strings in Zig?
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0x09
Can a plain *T be null in Zig?
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0x09
What does arr[2..] mean?
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0x09
How do you compare two strings in Zig?
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0x09
Can a plain *T be null in Zig?
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0x09
What does arr[2..] mean?
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0x0A
What does try foo() expand to?
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0x0A
defer vs errdefer?
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0x0A
In what order do multiple defers run?
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0x0A
E!T vs ?T?
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0x0A
Three ways to unwrap an optional opt?
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0x0A
What is an error return trace?
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0x0A
What does fn f() !void mean?
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0x0A
Why put errdefer right after an allocation?
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0x0A
How is Zig's error handling different from JavaScript exceptions?
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0x0A
When should you use an optional instead of an error?
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0x0A
How is Zig's error handling different from JavaScript exceptions?
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0x0A
When should you use an optional instead of an error?
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0x0B
Why does Zig pass allocators explicitly?
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0x0B
What is std.mem.Allocator internally?
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0x0B
alloc/free vs create/destroy?
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0x0B
When is an ArenaAllocator a good fit?
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0x0B
What does FixedBufferAllocator do?
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0x0B
Which allocator makes a test fail on a leak?
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0x0B
What was DebugAllocator called before Zig 0.14?
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0x0B
How do you append to a Zig 0.15 std.ArrayList?
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0x0B
Is memory from gpa.alloc zeroed?
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0x0B
Why can an ArenaAllocator skip individual frees?
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0x0B
Which error can every allocation return?
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0x0B
Is memory from gpa.alloc zeroed?
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0x0B
Why can an ArenaAllocator skip individual frees?
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0x0B
Which error can every allocation return?
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0x0C
How does Zig do generics?
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0x0C
What does @This() return?
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0x0C
Which features from other languages does comptime replace?
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0x0C
What is anytype?
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0x0C
Why use inline for?
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0x0C
Are container-level const initializers evaluated at compile time?
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0x0C
What does @typeInfo(T) give you?
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0x0C
What's the difference between compile time and runtime?
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0x0C
What does @field(p, "x") do?
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0x0C
What's the difference between compile time and runtime?
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0x0C
What does @field(p, "x") do?
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0x0D
How do you use a C header from Zig?
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0x0D
What is zig cc?
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0x0D
What does export fn do?
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0x0D
Bit layout of packed struct(u8) { a: bool, b: bool, rest: u6 }?
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0x0D
Why mark an MMIO pointer volatile?
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0x0D
How do you turn an integer address into a pointer in Zig?
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0x0D
What is [*c]T?
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0x0D
What is an ABI?
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0x0D
What is memory-mapped I/O?
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0x0D
What is an ABI?
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0x0D
What is memory-mapped I/O?
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