| ... | ... | @@ -5393,7 +5393,6 @@ pub fn parseU64(buf: []const u8, radix: u8) !u64 { |
| 5393 | 5393 | // x *= radix |
| 5394 | 5394 | var ov = @mulWithOverflow(x, radix); |
| 5395 | 5395 | if (ov[1] != 0) return error.OverFlow; |
| 5396 | | |
| 5397 | 5396 | |
| 5398 | 5397 | // x += digit |
| 5399 | 5398 | ov = @addWithOverflow(ov[0], digit); |
| ... | ... | @@ -6067,7 +6066,7 @@ struct Foo *do_a_thing(void) { |
| 6067 | 6066 | <p>Zig code</p> |
| 6068 | 6067 | {#syntax_block|zig|call_malloc_from_zig.zig#} |
| 6069 | 6068 | // malloc prototype included for reference |
| 6070 | | extern fn malloc(size: size_t) ?*u8; |
| 6069 | extern fn malloc(size: usize) ?*u8; |
| 6071 | 6070 | |
| 6072 | 6071 | fn doAThing() ?*Foo { |
| 6073 | 6072 | const ptr = malloc(1234) orelse return null; |
| ... | ... | @@ -7479,64 +7478,66 @@ pub fn syscall3(number: usize, arg1: usize, arg2: usize, arg3: usize) usize { |
| 7479 | 7478 | <p> |
| 7480 | 7479 | Dissecting the syntax: |
| 7481 | 7480 | </p> |
| 7482 | | {#syntax_block|zig|Assembly Syntax Explained#} |
| 7483 | | // Inline assembly is an expression which returns a value. |
| 7484 | | // the `asm` keyword begins the expression. |
| 7485 | | _ = asm |
| 7486 | | // `volatile` is an optional modifier that tells Zig this |
| 7487 | | // inline assembly expression has side-effects. Without |
| 7488 | | // `volatile`, Zig is allowed to delete the inline assembly |
| 7489 | | // code if the result is unused. |
| 7490 | | volatile ( |
| 7491 | | // Next is a comptime string which is the assembly code. |
| 7492 | | // Inside this string one may use `%[ret]`, `%[number]`, |
| 7493 | | // or `%[arg1]` where a register is expected, to specify |
| 7494 | | // the register that Zig uses for the argument or return value, |
| 7495 | | // if the register constraint strings are used. However in |
| 7496 | | // the below code, this is not used. A literal `%` can be |
| 7497 | | // obtained by escaping it with a double percent: `%%`. |
| 7498 | | // Often multiline string syntax comes in handy here. |
| 7481 | {#code_begin|syntax|Assembly Syntax Explained#} |
| 7482 | pub fn syscall1(number: usize, arg1: usize) usize { |
| 7483 | // Inline assembly is an expression which returns a value. |
| 7484 | // the `asm` keyword begins the expression. |
| 7485 | return asm |
| 7486 | // `volatile` is an optional modifier that tells Zig this |
| 7487 | // inline assembly expression has side-effects. Without |
| 7488 | // `volatile`, Zig is allowed to delete the inline assembly |
| 7489 | // code if the result is unused. |
| 7490 | volatile ( |
| 7491 | // Next is a comptime string which is the assembly code. |
| 7492 | // Inside this string one may use `%[ret]`, `%[number]`, |
| 7493 | // or `%[arg1]` where a register is expected, to specify |
| 7494 | // the register that Zig uses for the argument or return value, |
| 7495 | // if the register constraint strings are used. However in |
| 7496 | // the below code, this is not used. A literal `%` can be |
| 7497 | // obtained by escaping it with a double percent: `%%`. |
| 7498 | // Often multiline string syntax comes in handy here. |
| 7499 | 7499 | \\syscall |
| 7500 | | // Next is the output. It is possible in the future Zig will |
| 7501 | | // support multiple outputs, depending on how |
| 7502 | | // https://github.com/ziglang/zig/issues/215 is resolved. |
| 7503 | | // It is allowed for there to be no outputs, in which case |
| 7504 | | // this colon would be directly followed by the colon for the inputs. |
| 7505 | | : |
| 7506 | | // This specifies the name to be used in `%[ret]` syntax in |
| 7507 | | // the above assembly string. This example does not use it, |
| 7508 | | // but the syntax is mandatory. |
| 7509 | | [ret] |
| 7510 | | // Next is the output constraint string. This feature is still |
| 7511 | | // considered unstable in Zig, and so LLVM/GCC documentation |
| 7512 | | // must be used to understand the semantics. |
| 7513 | | // http://releases.llvm.org/10.0.0/docs/LangRef.html#inline-asm-constraint-string |
| 7514 | | // https://gcc.gnu.org/onlinedocs/gcc/Extended-Asm.html |
| 7515 | | // In this example, the constraint string means "the result value of |
| 7516 | | // this inline assembly instruction is whatever is in $rax". |
| 7517 | | "={rax}" |
| 7518 | | // Next is either a value binding, or `->` and then a type. The |
| 7519 | | // type is the result type of the inline assembly expression. |
| 7520 | | // If it is a value binding, then `%[ret]` syntax would be used |
| 7521 | | // to refer to the register bound to the value. |
| 7522 | | (-> usize) |
| 7523 | | // Next is the list of inputs. |
| 7524 | | // The constraint for these inputs means, "when the assembly code is |
| 7525 | | // executed, $rax shall have the value of `number` and $rdi shall have |
| 7526 | | // the value of `arg1`". Any number of input parameters is allowed, |
| 7527 | | // including none. |
| 7528 | | : [number] "{rax}" (number), |
| 7529 | | [arg1] "{rdi}" (arg1) |
| 7530 | | // Next is the list of clobbers. These declare a set of registers whose |
| 7531 | | // values will not be preserved by the execution of this assembly code. |
| 7532 | | // These do not include output or input registers. The special clobber |
| 7533 | | // value of "memory" means that the assembly writes to arbitrary undeclared |
| 7534 | | // memory locations - not only the memory pointed to by a declared indirect |
| 7535 | | // output. In this example we list $rcx and $r11 because it is known the |
| 7536 | | // kernel syscall does not preserve these registers. |
| 7537 | | : "rcx", "r11" |
| 7538 | | ); |
| 7539 | | {#end_syntax_block#} |
| 7500 | // Next is the output. It is possible in the future Zig will |
| 7501 | // support multiple outputs, depending on how |
| 7502 | // https://github.com/ziglang/zig/issues/215 is resolved. |
| 7503 | // It is allowed for there to be no outputs, in which case |
| 7504 | // this colon would be directly followed by the colon for the inputs. |
| 7505 | : |
| 7506 | // This specifies the name to be used in `%[ret]` syntax in |
| 7507 | // the above assembly string. This example does not use it, |
| 7508 | // but the syntax is mandatory. |
| 7509 | [ret] |
| 7510 | // Next is the output constraint string. This feature is still |
| 7511 | // considered unstable in Zig, and so LLVM/GCC documentation |
| 7512 | // must be used to understand the semantics. |
| 7513 | // http://releases.llvm.org/10.0.0/docs/LangRef.html#inline-asm-constraint-string |
| 7514 | // https://gcc.gnu.org/onlinedocs/gcc/Extended-Asm.html |
| 7515 | // In this example, the constraint string means "the result value of |
| 7516 | // this inline assembly instruction is whatever is in $rax". |
| 7517 | "={rax}" |
| 7518 | // Next is either a value binding, or `->` and then a type. The |
| 7519 | // type is the result type of the inline assembly expression. |
| 7520 | // If it is a value binding, then `%[ret]` syntax would be used |
| 7521 | // to refer to the register bound to the value. |
| 7522 | (-> usize) |
| 7523 | // Next is the list of inputs. |
| 7524 | // The constraint for these inputs means, "when the assembly code is |
| 7525 | // executed, $rax shall have the value of `number` and $rdi shall have |
| 7526 | // the value of `arg1`". Any number of input parameters is allowed, |
| 7527 | // including none. |
| 7528 | : [number] "{rax}" (number), |
| 7529 | [arg1] "{rdi}" (arg1) |
| 7530 | // Next is the list of clobbers. These declare a set of registers whose |
| 7531 | // values will not be preserved by the execution of this assembly code. |
| 7532 | // These do not include output or input registers. The special clobber |
| 7533 | // value of "memory" means that the assembly writes to arbitrary undeclared |
| 7534 | // memory locations - not only the memory pointed to by a declared indirect |
| 7535 | // output. In this example we list $rcx and $r11 because it is known the |
| 7536 | // kernel syscall does not preserve these registers. |
| 7537 | : "rcx", "r11" |
| 7538 | ); |
| 7539 | } |
| 7540 | {#code_end#} |
| 7540 | 7541 | <p> |
| 7541 | 7542 | For x86 and x86_64 targets, the syntax is AT&T syntax, rather than the more |
| 7542 | 7543 | popular Intel syntax. This is due to technical constraints; assembly parsing is |
| ... | ... | @@ -7892,7 +7893,7 @@ fn add(a: i32, b: i32) i32 { |
| 7892 | 7893 | {#syntax#}@call{#endsyntax#} allows more flexibility than normal function call syntax does. The |
| 7893 | 7894 | {#syntax#}CallModifier{#endsyntax#} enum is reproduced here: |
| 7894 | 7895 | </p> |
| 7895 | | {#syntax_block|zig|builtin.CallModifier struct#} |
| 7896 | {#code_begin|syntax|builtin.CallModifier struct#} |
| 7896 | 7897 | pub const CallModifier = enum { |
| 7897 | 7898 | /// Equivalent to function call syntax. |
| 7898 | 7899 | auto, |
| ... | ... | @@ -7926,7 +7927,7 @@ pub const CallModifier = enum { |
| 7926 | 7927 | /// compile-time, a compile error is emitted instead. |
| 7927 | 7928 | compile_time, |
| 7928 | 7929 | }; |
| 7929 | | {#end_syntax_block#} |
| 7930 | {#code_end#} |
| 7930 | 7931 | {#header_close#} |
| 7931 | 7932 | |
| 7932 | 7933 | {#header_open|@cDefine#} |
Manlio Perillo <manlio.perillo@gmail.com> 2023-02-11 11:29:36+01:00
Veikka Tuominen <git@vexu.eu> 2023-02-13 16:21:54+02:00