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kateinoigakukunkateinoigakukun
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wit-component: Allow cabi_realloc to be weakly defined (#1625)
If a weak "default" visibility symbol is defined in a shared library, wasm-ld emits an import for the symbol for the "env" module for the case where the symbol is overridden by other modules. `cabi_realloc` is usually defined weakly by wit-bindgen'ed code, and if the code is compiled with `-fvisibility=default`, it emits an import for "env.cabi_realloc". The import leads re-exporting the symbol to the "env" module, and it conflicts with the special re-exporting logic for `cabi_realloc`. This commit fixes the duplicate re-exporting issue.
1 parent 85270ca commit 02d291a

5 files changed

Lines changed: 167 additions & 4 deletions

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‎crates/wit-component/src/linking.rs‎

Lines changed: 23 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -1046,14 +1046,19 @@ fn find_dependencies(
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}
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}
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1049+
struct EnvFunctionExports<'a> {
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exports: Vec<(&'a str, &'a FunctionType, usize)>,
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reexport_cabi_realloc: bool,
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}
1053+
10491054
/// Analyze the specified metadata and generate a list of functions which should be re-exported as a
10501055
/// `call.indirect`-based function by the main (AKA "env") module, including the offset of the library containing
10511056
/// the original export.
10521057
fn env_function_exports<'a>(
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metadata: &'a [Metadata<'a>],
10541059
exporters: &'a IndexMap<&'a ExportKey, (&'a str, &Export)>,
10551060
topo_sorted: &[usize],
1056-
) -> Result<Vec<(&'a str, &'a FunctionType, usize)>> {
1061+
) -> Result<EnvFunctionExports<'a>> {
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let function_exporters = exporters
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.iter()
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.filter_map(|(export, exporter)| {
@@ -1103,7 +1108,12 @@ fn env_function_exports<'a>(
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seen.insert(index);
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}
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1106-
Ok(result)
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let reexport_cabi_realloc = exported.contains("cabi_realloc");
1112+
1113+
Ok(EnvFunctionExports {
1114+
exports: result,
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reexport_cabi_realloc,
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})
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}
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11091119
/// Synthesize a module which contains trapping stub exports for the specified functions.
@@ -1385,12 +1395,21 @@ impl Linker {
13851395

13861396
let topo_sorted = topo_sort(metadata.len(), &dependencies)?;
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1388-
let env_function_exports = env_function_exports(&metadata, &exporters, &topo_sorted)?;
1398+
let EnvFunctionExports {
1399+
exports: env_function_exports,
1400+
reexport_cabi_realloc,
1401+
} = env_function_exports(&metadata, &exporters, &topo_sorted)?;
13891402

13901403
let (env_module, dl_openables, table_base) = make_env_module(
13911404
&metadata,
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&env_function_exports,
1393-
cabi_realloc_exporter,
1406+
if reexport_cabi_realloc {
1407+
// If "env" module already reexports "cabi_realloc", we don't need to
1408+
// reexport it again.
1409+
None
1410+
} else {
1411+
cabi_realloc_exporter
1412+
},
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self.stack_size.unwrap_or(DEFAULT_STACK_SIZE_BYTES),
13951414
);
13961415

‎crates/wit-component/tests/components/link-weak-cabi-realloc/component.wat‎

Lines changed: 116 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,116 @@
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(component
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(core module (;0;)
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(type (;0;) (func (param i32 i32 i32 i32) (result i32)))
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(func (;0;) (type 0) (param i32 i32 i32 i32) (result i32)
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local.get 0
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local.get 1
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local.get 2
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local.get 3
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i32.const 1
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call_indirect (type 0)
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)
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(table (;0;) 2 funcref)
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(memory (;0;) 17)
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(global (;0;) (mut i32) i32.const 1048576)
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(global (;1;) i32 i32.const 1048592)
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(global (;2;) i32 i32.const 1)
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(global (;3;) (mut i32) i32.const 1048592)
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(global (;4;) (mut i32) i32.const 1114112)
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(export "__stack_pointer" (global 0))
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(export "foo:memory_base" (global 1))
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(export "foo:table_base" (global 2))
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(export "__heap_base" (global 3))
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(export "__heap_end" (global 4))
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(export "cabi_realloc" (func 0))
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(export "__indirect_function_table" (table 0))
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(export "memory" (memory 0))
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(@producers
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(processed-by "wit-component" "$CARGO_PKG_VERSION")
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)
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)
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(core module (;1;)
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(@dylink.0
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(mem-info (memory 0 4))
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)
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(type (;0;) (func (param i32 i32 i32 i32) (result i32)))
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(type (;1;) (func (param i32)))
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(type (;2;) (func (param i32 i32)))
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(import "env" "cabi_realloc" (func $cabi_realloc.0 (;0;) (type 0)))
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(func $cabi_realloc.1 (;1;) (type 0) (param i32 i32 i32 i32) (result i32)
40+
i32.const -257976192
41+
)
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(func $foo (;2;) (type 2) (param i32 i32))
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(export "cabi_realloc" (func $cabi_realloc.1))
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(export "test:test/test#foo" (func $foo))
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)
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(core module (;2;)
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(type (;0;) (func))
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(type (;1;) (func (param i32)))
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(type (;2;) (func (param i32 i32 i32 i32) (result i32)))
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(import "env" "memory" (memory (;0;) 0))
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(import "env" "__indirect_function_table" (table (;0;) 0 funcref))
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(import "foo" "cabi_realloc" (func (;0;) (type 2)))
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(func (;1;) (type 0))
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(start 1)
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(elem (;0;) (i32.const 1) func)
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(elem (;1;) (i32.const 1) func 0)
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(data (;0;) (i32.const 1048576) "\00\00\00\00\00\00\10\00")
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(@producers
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(processed-by "wit-component" "$CARGO_PKG_VERSION")
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)
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)
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(core instance (;0;) (instantiate 0))
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(alias core export 0 "memory" (core memory (;0;)))
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(alias core export 0 "cabi_realloc" (core func (;0;)))
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(alias core export 0 "__heap_base" (core global (;0;)))
66+
(alias core export 0 "__heap_end" (core global (;1;)))
67+
(core instance (;1;)
68+
(export "__heap_base" (global 0))
69+
(export "__heap_end" (global 1))
70+
)
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(core instance (;2;))
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(alias core export 0 "memory" (core memory (;1;)))
73+
(alias core export 0 "__indirect_function_table" (core table (;0;)))
74+
(alias core export 0 "__stack_pointer" (core global (;2;)))
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(alias core export 0 "foo:memory_base" (core global (;3;)))
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(alias core export 0 "foo:table_base" (core global (;4;)))
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(alias core export 0 "cabi_realloc" (core func (;1;)))
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(core instance (;3;)
79+
(export "memory" (memory 1))
80+
(export "__indirect_function_table" (table 0))
81+
(export "__stack_pointer" (global 2))
82+
(export "__memory_base" (global 3))
83+
(export "__table_base" (global 4))
84+
(export "cabi_realloc" (func 1))
85+
)
86+
(core instance (;4;) (instantiate 1
87+
(with "GOT.mem" (instance 1))
88+
(with "GOT.func" (instance 2))
89+
(with "env" (instance 3))
90+
)
91+
)
92+
(alias core export 4 "cabi_realloc" (core func (;2;)))
93+
(alias core export 4 "cabi_realloc" (core func (;3;)))
94+
(core instance (;5;) (instantiate 2
95+
(with "env" (instance 0))
96+
(with "foo" (instance 4))
97+
)
98+
)
99+
(type (;0;) (func (param "x" string)))
100+
(alias core export 4 "test:test/test#foo" (core func (;4;)))
101+
(func (;0;) (type 0) (canon lift (core func 4) (memory 0) (realloc 2) string-encoding=utf8))
102+
(component (;0;)
103+
(type (;0;) (func (param "x" string)))
104+
(import "import-func-foo" (func (;0;) (type 0)))
105+
(type (;1;) (func (param "x" string)))
106+
(export (;1;) "foo" (func 0) (func (type 1)))
107+
)
108+
(instance (;0;) (instantiate 0
109+
(with "import-func-foo" (func 0))
110+
)
111+
)
112+
(export (;1;) "test:test/test" (instance 0))
113+
(@producers
114+
(processed-by "wit-component" "$CARGO_PKG_VERSION")
115+
)
116+
)

‎crates/wit-component/tests/components/link-weak-cabi-realloc/component.wit.print‎

Lines changed: 5 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,5 @@
1+
package root:component;
2+
3+
world root {
4+
export test:test/test;
5+
}

‎crates/wit-component/tests/components/link-weak-cabi-realloc/lib-foo.wat‎

Lines changed: 14 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,14 @@
1+
(module
2+
(@dylink.0
3+
(mem-info (memory 0 4))
4+
)
5+
(type (func (param i32 i32 i32 i32) (result i32)))
6+
(type (func (param i32)))
7+
(import "env" "cabi_realloc" (func $cabi_realloc.0 (type 0)))
8+
(func $cabi_realloc.1 (type 0)
9+
i32.const 0xf09f9880
10+
)
11+
(func $foo (param i32 i32))
12+
(export "cabi_realloc" (func $cabi_realloc.1))
13+
(export "test:test/test#foo" (func $foo))
14+
)

‎crates/wit-component/tests/components/link-weak-cabi-realloc/lib-foo.wit‎

Lines changed: 9 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,9 @@
1+
package test:test;
2+
3+
interface test {
4+
foo: func(x: string);
5+
}
6+
7+
world lib-foo {
8+
export test;
9+
}

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