| author |  Alex Kladov <aleksey.kladov@gmail.com> 2025-07-14 16:12:55+01:00 |
| committer | Alex Kladov <aleksey.kladov@gmail.com> 2025-07-14 16:20:33+01:00 |
| log | d045eb7a4af758e3483e5e8fd9bdbe725095fdec |
| tree | c2152dcc517ab6555cd215430b28801eb30fee01 |
| parent | f43f89a70588c2add2a7c84d12eef2852d215f51 |
langref: make example more interesting.
As written, I think langref's example is actually a poor reason to use
`inline`.
If you have
if (foo(1200, 34) != 1234) {
@compileError("bad");
}
and you want to make sure that the call is executed at compile time, the
right way to fix it is to add comptime
if (comptime foo(1200, 34) != 1234) {
@compileError("bad");
}
and not to make the function `inline`. I _think_ that inlining functions
just to avoid `comptime` at a call-site is an anti-pattern. When the
reader sees `foo(123)` at the call-site, they _expect_ this to be a
runtime call, as that's the normal rule in Zig.
Inline is still necessary when you can't make the _whole_ call
`comptime`, because it has some runtime effects, but you still want
comptime-known result.
A good example here is
inline fn findImportPkgHashOrFatal(b: *Build, comptime asking_build_zig: type, comptime dep_name: []const u8) []const u8 {
from Build.zig, where the `b` argument is runtime, and is used for
side-effects, but where the result is comptime.
I don't know of a good small example to demonstrate the subtelty here,
so I went ahead with just adding a runtime print to `foo`. Hopefully
it'll be enough for motivated reader to appreciate the subtelty!1 files changed, 3 insertions(+), 0 deletions(-)
doc- langref
doc/langref/inline_call.zig+3
| ... | @@ -1,3 +1,5 @@ | ... | @@ -1,3 +1,5 @@ |
| 1 | const std = @import("std"); | ||
| 2 | |||
| 1 | test "inline function call" { | 3 | test "inline function call" { |
| 2 | if (foo(1200, 34) != 1234) { | 4 | if (foo(1200, 34) != 1234) { |
| 3 | @compileError("bad"); | 5 | @compileError("bad"); |
| ... | @@ -5,6 +7,7 @@ test "inline function call" { | ... | @@ -5,6 +7,7 @@ test "inline function call" { |
| 5 | } | 7 | } |
| 6 | 8 | ||
| 7 | inline fn foo(a: i32, b: i32) i32 { | 9 | inline fn foo(a: i32, b: i32) i32 { |
| 10 | std.debug.print("runtime a = {} b = {}", .{ a, b }); | ||
| 8 | return a + b; | 11 | return a + b; |
| 9 | } | 12 | } |
| 10 | 13 |