Target modifiers (special marked options) are recorded in metainfo #133138

azhogin · 2024-11-17T21:27:33Z

Target modifiers (special marked options) are recorded in metainfo and compared to be equal in different linked crates.

Draft PR for this RFC: rust-lang/rfcs#3716

Option may be marked as TMOD, example: regparm: Option<u32> = (None, parse_opt_number, [TRACKED TMOD].
If an TMOD-marked option has non-default value, it will be recorded in crate metainfo as a Vec<String> of "Option=Value" strings.

Option value is generated using Debug trait.

Error example:

error: crate `incompatible_regparm` has incompatible target modifier with extern crate `wrong_regparm`: `regparm = ( Some(1) | Some(2) )`
  --> $DIR/incompatible_regparm.rs:5:1
   |
LL | #![no_core]
   | ^
   |
   = note: `#[deny(incompatible_target_modifiers)]` on by default

error: aborting due to 1 previous error

rustbot · 2024-11-17T21:27:42Z

r? @davidtwco

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…d compared to be equal in different crates

davidtwco · 2024-11-21T10:52:40Z

compiler/rustc_metadata/src/creader.rs

+        if let Some(vec) = &sess.opts.cg.unsafe_allow_abi_mismatch
+            && vec.is_empty()
+        {
+            return;
+        }


Given that you check access unsafe_allow_abi_mismatch later, maybe do something like this:

Suggested change

if let Some(vec) = &sess.opts.cg.unsafe_allow_abi_mismatch

&& vec.is_empty()

{

return;

}

let allowed_flag_mismatches = sets.opts.cg.unsafe_allow_abi_mismatch.as_ref().unwrap_or_default();

if allowed_flag_mismatches.is_empty() {

// Setting `-Zunsafe-allow-abi-mismatch=` to an empty

// value allows all target modifier mismatches.

return;

}

..and then use allowed_flag_mismatches after this.

(that suggestion might not compile exactly, but you should be able to do something like it)

davidtwco · 2024-11-21T10:54:05Z

compiler/rustc_session/src/options.rs

@@ -58,10 +58,58 @@ macro_rules! hash_substruct {
    };
 }

+macro_rules! gather_tmods {
+    ($_opt_name:ident, $init:expr, $opt_expr:expr, $mods:expr, [SUBSTRUCT], [TMOD]) => {
+        compile_error!("SUBSTRUCT can't be TMOD (target modifier)");


Can you just use "target modifier" without the TMOD abbreviation throughout?

davidtwco · 2024-11-21T10:55:34Z

compiler/rustc_metadata/src/creader.rs

+        if let Some(vec) = &sess.opts.cg.unsafe_allow_abi_mismatch
+            && vec.is_empty()
+        {
+            return;


Do we want to allow users to opt-out of all mismatches?

davidtwco · 2024-11-21T10:57:04Z

compiler/rustc_session/src/options.rs

+        v: Option<&str>,
+    ) -> bool {
+        match v {
+            Some(s) => {


can you call parse_opt_comma_list in this branch and re-use that code?

davidtwco · 2024-11-21T11:06:00Z

compiler/rustc_lint/messages.ftl

+lint_incompatible_target_modifiers =
+    mixing `{$flag_name_suffixed}` will cause an ABI mismatch
+    .note1 = `{$flag_name_suffixed}`=`{$flag_local_value}` in crate `{$local_crate}`, `{$flag_name_suffixed}`=`{$flag_extern_value}` in crate `{$extern_crate}`
+    .help = This error occurs because the `{$flag_name_suffixed}` flag modifies the ABI,


Ideally this should say something like:

Suggested change

.help = This error occurs because the `{$flag_name_suffixed}` flag modifies the ABI,

.help = `{$flag_name_suffixed}` modifies the ABI and Rust crates compiled with different values of this flag cannot be used together safely

It would be good if we could provide the whole option, not just the name, so -Zregparm rather than regparm.

davidtwco · 2024-11-21T11:25:08Z

compiler/rustc_session/src/options.rs

 macro_rules! top_level_options {
    ( $( #[$top_level_attr:meta] )* pub struct Options { $(
        $( #[$attr:meta] )*
-        $opt:ident : $t:ty [$dep_tracking_marker:ident],
+        $opt:ident : $t:ty [$dep_tracking_marker:ident $( $tmod:ident )*],


Is the $( )* just because it can be optional? Can you use ? instead?

davidtwco · 2024-11-21T11:26:04Z

compiler/rustc_session/src/options.rs

+        compile_error!("SUBSTRUCT can't be TMOD (target modifier)");
+    };
+    ($opt_name:ident, $opt_expr:expr, $mods:expr, [UNTRACKED], [TMOD]) => {
+        compile_error!("Top level option can't be TMOD (target modifier)");


davidtwco · 2024-11-21T11:28:16Z

compiler/rustc_session/src/options.rs

+        compile_error!("SUBSTRUCT can't be TMOD (target modifier)");
+    };
+    ($opt_name:ident, $init:expr, $opt_expr:expr, $mods:expr, [UNTRACKED], [TMOD]) => {
+        if *$opt_expr != $init {


Shouldn't we also record a target modifier set to its default value?

davidtwco · 2024-11-21T11:29:24Z

compiler/rustc_session/src/options.rs

+    };
+    ($opt_name:ident, $init:expr, $opt_expr:expr, $mods:expr, [UNTRACKED], [TMOD]) => {
+        if *$opt_expr != $init {
+            $mods.push(format!("{}={:?}", stringify!($opt_name), $opt_expr));


We should avoid storing things like Some(1) or CodeModel::Small or w/e here and instead store whatever the user wrote, since that's what we'll want to show to them.

davidtwco · 2024-11-21T11:32:41Z

tests/ui/target_modifiers/incompatible_regparm.rs

+#![no_core]
+#![feature(no_core, lang_items, repr_simd)]
+
+#![cfg_attr(allow_attr, allow(incompatible_target_modifiers))]


Do we want to support this?

rustbot assigned davidtwco Nov 17, 2024

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Nov 17, 2024

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azhogin force-pushed the azhogin/target-modifiers branch from d99ff62 to bd52a23 Compare November 18, 2024 19:21

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azhogin force-pushed the azhogin/target-modifiers branch from bd52a23 to 500600b Compare November 18, 2024 22:37

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azhogin force-pushed the azhogin/target-modifiers branch 2 times, most recently from db91299 to 43e5956 Compare November 20, 2024 22:32

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Target modifiers (special marked options) are recorded in metainfo an…

6793451

…d compared to be equal in different crates

azhogin force-pushed the azhogin/target-modifiers branch from 43e5956 to 6793451 Compare November 21, 2024 10:31

davidtwco requested changes Nov 21, 2024

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rustbot added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Nov 21, 2024

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Target modifiers (special marked options) are recorded in metainfo #133138

Target modifiers (special marked options) are recorded in metainfo #133138

azhogin commented Nov 17, 2024

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davidtwco Nov 21, 2024

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davidtwco Nov 21, 2024

davidtwco Nov 21, 2024

-        if let Some(vec) = &sess.opts.cg.unsafe_allow_abi_mismatch
-            && vec.is_empty()
-        {
-            return;
-        }
+        let allowed_flag_mismatches = sets.opts.cg.unsafe_allow_abi_mismatch.as_ref().unwrap_or_default();
+        if allowed_flag_mismatches.is_empty() {
+            // Setting `-Zunsafe-allow-abi-mismatch=` to an empty
+            // value allows all target modifier mismatches.
+            return;
+        }

	.help = This error occurs because the `{$flag_name_suffixed}` flag modifies the ABI,
	.help = `{$flag_name_suffixed}` modifies the ABI and Rust crates compiled with different values of this flag cannot be used together safely

Target modifiers (special marked options) are recorded in metainfo #133138

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Target modifiers (special marked options) are recorded in metainfo #133138

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