rrbutani

see https://www.gnu.org/software/make/manual/html_node/General-Search.html

from the perspective of a recipe (i.e. automatic variables), prerequisites are "rewritten"; if they're resolved to a directory in VPATH, the prereq is prefixed with that directory

rrbutani

see here for .section directive flags and _type_s

• also see the solaris ELF object file format docs

https://c.godbolt.org/z/T4j9GP91n https://assembly.godbolt.org/z/TGnGMWWWd

conflicting linker section flags?

i.e.:

rrbutani

see:

• https://ninja-build.org/manual.html#ref_dependencies
• https://fuchsia.dev/fuchsia-src/development/build/ninja_how#order-only_inputs
• https://github.com/ninja-build/ninja/blob/d60673d49e4facef8579eebeb818318c5b744b0b/src/graph.h#L239-L240
• https://www.gnu.org/software/make/manual/html_node/Prerequisite-Types.html

semantics of order-only deps:

• when deciding whether to rebuild a target, the mtimes (or existence) of order-only deps are not considered
• if the target is built (i.e. due to a normal prereq that was newer), it will wait on order-only deps
• even if the target is not built (i.e. up to date), order-only deps will be scheduled for building (if out of date)

rrbutani

see comment in Makefile

rrbutani

what

tests the we can "project" particular files out of a TreeArtifact for consumption in downstream rules

the intent is that by doing this projection:

• downstream rules that operate on files (not directories — i.e. not TreeArtifact aware) can consume our artifact
• sensitivity in downstream targets is narrowed to only the files in the TreeArtifact that are projected out

rrbutani

0: [.]      succ(a,  ): add `1` to `a`
1: [+]       add(a, b): ret = a; ret =       succ(ret)    `b`     times
2: [*]       mul(a, b): ret = 0; ret =        add(ret, a) `b`     times
3: [^]       exp(a, b): ret = 1; ret =        mul(ret, a) `b`     times
4: [!] tetration(a, b): ret = a; ret =        exp(ret, a) `b - 1` times (special case b = 0 -> 1)
5: [@] pentation(a, b): ret = a; ret =  tetration(ret, a) `b - 1` times (special case b = 0 -> 1)
6: [#]  hexation(a, b): ret = a; ret =  pentation(ret, a) `b - 1` times (special case b = 0 -> 1)

3 .   -> 4
3 + 4 -> 7                 { ((((3 .  ) .  ) .  ) .  ) }

rrbutani

use std::{
    cell::UnsafeCell,
    marker::PhantomData,
    sync::{
        OnceLock,
        mpsc::{Receiver, Sender, channel},
    },
};

// initialized from thread that can call ui stuff

rrbutani

We couldn’t find that file to show.

rrbutani

takeaways:

• actions made by an aspect get to make files in the package of the target they are visiting
• have "anonymous" action-like semantics, kind of
  • will not get built multiple times if the same aspect for the same target is requested by two different consuming rules

bazel build //:yo @foo//:all

rrbutani

Background

See this gist about post-hoc action input pruning and the limitations w.r.t to caching.

buck2 has starlark APIs for (limited) dynamic deps (i.e. dynamic action creation albeit only with input subsetting): https://buck2.build/docs/rule_authors/dynamic_dependencies/

Bazel's internal dependency engine (skyframe) is capable of representing such dependencies and internal rulesets make use of this functionality (i.e. ThinLTO and C++20 module support in rules_cc) however — starlark rules have no way to express such graphs.

This PoC