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Demangle Rust's Y<type><path> production for passably simple <type>s.
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PiperOrigin-RevId: 633229582
Change-Id: Ibda908d261b52b1af766304992edd77a5bdd56b5
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@copybara-github
Chris Mihelich authored and copybara-github committed May 13, 2024
1 parent 99bb2f6 commit 692d9e5
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Showing 3 changed files with 229 additions and 6 deletions.
145 changes: 143 additions & 2 deletions absl/debugging/internal/demangle_rust.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -37,6 +37,33 @@ bool IsUpper(char c) { return 'A' <= c && c <= 'Z'; }
bool IsAlpha(char c) { return IsLower(c) || IsUpper(c); }
bool IsIdentifierChar(char c) { return IsAlpha(c) || IsDigit(c) || c == '_'; }

const char* BasicTypeName(char c) {
switch (c) {
case 'a': return "i8";
case 'b': return "bool";
case 'c': return "char";
case 'd': return "f64";
case 'e': return "str";
case 'f': return "f32";
case 'h': return "u8";
case 'i': return "isize";
case 'j': return "usize";
case 'l': return "i32";
case 'm': return "u32";
case 'n': return "i128";
case 'o': return "u128";
case 'p': return "_";
case 's': return "i16";
case 't': return "u16";
case 'u': return "()";
case 'v': return "...";
case 'x': return "i64";
case 'y': return "u64";
case 'z': return "!";
}
return nullptr;
}

// Parser for Rust symbol mangling v0, whose grammar is defined here:
//
// https://doc.rust-lang.org/rustc/symbol-mangling/v0.html#symbol-grammar-summary
Expand Down Expand Up @@ -115,12 +142,16 @@ class RustSymbolParser {

// path -> crate-root | inherent-impl | trait-impl | trait-definition |
// nested-path | generic-args | backref
//
// Note that ABSL_DEMANGLER_RECURSE does not work inside a nested switch
// (which would hide the generated case label). Thus we jump out of the
// inner switch with gotos before performing any fake recursion.
path:
switch (Take()) {
case 'C': goto crate_root;
case 'M': return false; // inherent-impl not yet implemented
case 'X': return false; // trait-impl not yet implemented
case 'Y': return false; // trait-definition not yet implemented
case 'Y': goto trait_definition;
case 'N': goto nested_path;
case 'I': return false; // generic-args not yet implemented
case 'B': return false; // backref not yet implemented
Expand All @@ -132,7 +163,16 @@ class RustSymbolParser {
if (!ParseIdentifier()) return false;
continue;

// nested-path -> N namespace path identifier (N consumed above)
// trait-definition -> Y type path (Y already consumed)
trait_definition:
if (!Emit("<")) return false;
ABSL_DEMANGLER_RECURSE(type, kTraitDefinitionInfix);
if (!Emit(" as ")) return false;
ABSL_DEMANGLER_RECURSE(path, kTraitDefinitionEnding);
if (!Emit(">")) return false;
continue;

// nested-path -> N namespace path identifier (N already consumed)
// namespace -> lower | upper
nested_path:
// Uppercase namespaces must be saved on the stack so we can print
Expand All @@ -156,6 +196,98 @@ class RustSymbolParser {

// Neither upper or lower
return false;

// type -> basic-type | array-type | slice-type | tuple-type |
// ref-type | mut-ref-type | const-ptr-type | mut-ptr-type |
// fn-type | dyn-trait-type | path | backref
//
// We use ifs instead of switch (Take()) because the default case jumps
// to path, which will need to see the first character not yet Taken
// from the input. Because we do not use a nested switch here,
// ABSL_DEMANGLER_RECURSE works fine in the 'S' case.
type:
if (IsLower(Peek())) {
const char* type_name = BasicTypeName(Take());
if (type_name == nullptr || !Emit(type_name)) return false;
continue;
}
if (Eat('A')) return false; // array-type not yet implemented
if (Eat('S')) {
if (!Emit("[")) return false;
ABSL_DEMANGLER_RECURSE(type, kSliceEnding);
if (!Emit("]")) return false;
continue;
}
if (Eat('T')) goto tuple_type;
if (Eat('R')) {
if (!Emit("&")) return false;
if (Eat('L')) return false; // lifetime not yet implemented
goto type;
}
if (Eat('Q')) {
if (!Emit("&mut ")) return false;
if (Eat('L')) return false; // lifetime not yet implemented
goto type;
}
if (Eat('P')) {
if (!Emit("*const ")) return false;
goto type;
}
if (Eat('O')) {
if (!Emit("*mut ")) return false;
goto type;
}
if (Eat('F')) return false; // fn-type not yet implemented
if (Eat('D')) return false; // dyn-trait-type not yet implemented
if (Eat('B')) return false; // backref not yet implemented
goto path;

// tuple-type -> T type* E (T already consumed)
tuple_type:
if (!Emit("(")) return false;

// The toolchain should call the unit type u instead of TE, but the
// grammar and other demanglers also recognize TE, so we do too.
if (Eat('E')) {
if (!Emit(")")) return false;
continue;
}

// A tuple with one element is rendered (type,) instead of (type).
ABSL_DEMANGLER_RECURSE(type, kAfterFirstTupleElement);
if (Eat('E')) {
if (!Emit(",)")) return false;
continue;
}

// A tuple with two elements is of course (x, y).
if (!Emit(", ")) return false;
ABSL_DEMANGLER_RECURSE(type, kAfterSecondTupleElement);
if (Eat('E')) {
if (!Emit(")")) return false;
continue;
}

// And (x, y, z) for three elements.
if (!Emit(", ")) return false;
ABSL_DEMANGLER_RECURSE(type, kAfterThirdTupleElement);
if (Eat('E')) {
if (!Emit(")")) return false;
continue;
}

// For longer tuples we write (x, y, z, ...), printing none of the
// content of the fourth and later types. Thus we avoid exhausting
// output buffers and human readers' patience when some library has a
// long tuple as an implementation detail, without having to
// completely obfuscate all tuples.
if (!Emit(", ...)")) return false;
++silence_depth_;
while (!Eat('E')) {
ABSL_DEMANGLER_RECURSE(type, kAfterSubsequentTupleElement);
}
--silence_depth_;
continue;
}
}

Expand All @@ -169,6 +301,13 @@ class RustSymbolParser {
kVendorSpecificSuffix,
kIdentifierInUppercaseNamespace,
kIdentifierInLowercaseNamespace,
kTraitDefinitionInfix,
kTraitDefinitionEnding,
kSliceEnding,
kAfterFirstTupleElement,
kAfterSecondTupleElement,
kAfterThirdTupleElement,
kAfterSubsequentTupleElement,
};

// Element count for the stack_ array. A larger kStackSize accommodates more
Expand Down Expand Up @@ -320,6 +459,8 @@ class RustSymbolParser {

// Emit the beginnings of braced forms like {shim:vtable#0}.
if (uppercase_namespace == '\0') {
// Decoding of Punycode is not yet implemented. For now we emit
// "{Punycode ...}" with the raw encoding inside.
if (is_punycoded && !Emit("{Punycode ")) return false;
} else {
switch (uppercase_namespace) {
Expand Down
6 changes: 2 additions & 4 deletions absl/debugging/internal/demangle_rust.h
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Original file line number Diff line number Diff line change
Expand Up @@ -33,10 +33,8 @@ namespace debugging_internal {
// call-stack space. It is suitable for symbolizing stack traces in a signal
// handler.
//
// The demangling logic is under development. In this version of Abseil,
// DemangleRustSymbolEncoding parses a few simple kinds of symbol names, but
// nothing having backreferences in the input or angle brackets in the
// demangling, and it emits raw Punycode instead of the UTF-8 represented by it.
// The demangling logic is under development; search for "not yet implemented"
// in the .cc file to see where the gaps are.
bool DemangleRustSymbolEncoding(const char* mangled, char* out,
std::size_t out_size);

Expand Down
84 changes: 84 additions & 0 deletions absl/debugging/internal/demangle_rust_test.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -209,6 +209,90 @@ TEST(DemangleRust, NestedUppercaseNamespaces) {
"crate_name::{Y:y#2}::{X:x#3}::{closure#4}");
}

TEST(DemangleRust, TraitDefinition) {
EXPECT_DEMANGLING(
"_RNvYNvC7crate_a9my_structNvC7crate_b8my_trait1f",
"<crate_a::my_struct as crate_b::my_trait>::f");
}

TEST(DemangleRust, BasicTypeNames) {
EXPECT_DEMANGLING("_RNvYaNvC1c1t1f", "<i8 as c::t>::f");
EXPECT_DEMANGLING("_RNvYbNvC1c1t1f", "<bool as c::t>::f");
EXPECT_DEMANGLING("_RNvYcNvC1c1t1f", "<char as c::t>::f");
EXPECT_DEMANGLING("_RNvYdNvC1c1t1f", "<f64 as c::t>::f");
EXPECT_DEMANGLING("_RNvYeNvC1c1t1f", "<str as c::t>::f");
EXPECT_DEMANGLING("_RNvYfNvC1c1t1f", "<f32 as c::t>::f");
EXPECT_DEMANGLING("_RNvYhNvC1c1t1f", "<u8 as c::t>::f");
EXPECT_DEMANGLING("_RNvYiNvC1c1t1f", "<isize as c::t>::f");
EXPECT_DEMANGLING("_RNvYjNvC1c1t1f", "<usize as c::t>::f");
EXPECT_DEMANGLING("_RNvYlNvC1c1t1f", "<i32 as c::t>::f");
EXPECT_DEMANGLING("_RNvYmNvC1c1t1f", "<u32 as c::t>::f");
EXPECT_DEMANGLING("_RNvYnNvC1c1t1f", "<i128 as c::t>::f");
EXPECT_DEMANGLING("_RNvYoNvC1c1t1f", "<u128 as c::t>::f");
EXPECT_DEMANGLING("_RNvYpNvC1c1t1f", "<_ as c::t>::f");
EXPECT_DEMANGLING("_RNvYsNvC1c1t1f", "<i16 as c::t>::f");
EXPECT_DEMANGLING("_RNvYtNvC1c1t1f", "<u16 as c::t>::f");
EXPECT_DEMANGLING("_RNvYuNvC1c1t1f", "<() as c::t>::f");
EXPECT_DEMANGLING("_RNvYvNvC1c1t1f", "<... as c::t>::f");
EXPECT_DEMANGLING("_RNvYxNvC1c1t1f", "<i64 as c::t>::f");
EXPECT_DEMANGLING("_RNvYyNvC1c1t1f", "<u64 as c::t>::f");
EXPECT_DEMANGLING("_RNvYzNvC1c1t1f", "<! as c::t>::f");

EXPECT_DEMANGLING_FAILS("_RNvYkNvC1c1t1f");
}

TEST(DemangleRust, SliceTypes) {
EXPECT_DEMANGLING("_RNvYSlNvC1c1t1f", "<[i32] as c::t>::f");
EXPECT_DEMANGLING("_RNvYSNvC1d1sNvC1c1t1f", "<[d::s] as c::t>::f");
}

TEST(DemangleRust, ImmutableReferenceTypes) {
EXPECT_DEMANGLING("_RNvYRlNvC1c1t1f", "<&i32 as c::t>::f");
EXPECT_DEMANGLING("_RNvYRNvC1d1sNvC1c1t1f", "<&d::s as c::t>::f");
}

TEST(DemangleRust, MutableReferenceTypes) {
EXPECT_DEMANGLING("_RNvYQlNvC1c1t1f", "<&mut i32 as c::t>::f");
EXPECT_DEMANGLING("_RNvYQNvC1d1sNvC1c1t1f", "<&mut d::s as c::t>::f");
}

TEST(DemangleRust, ConstantRawPointerTypes) {
EXPECT_DEMANGLING("_RNvYPlNvC1c1t1f", "<*const i32 as c::t>::f");
EXPECT_DEMANGLING("_RNvYPNvC1d1sNvC1c1t1f", "<*const d::s as c::t>::f");
}

TEST(DemangleRust, MutableRawPointerTypes) {
EXPECT_DEMANGLING("_RNvYOlNvC1c1t1f", "<*mut i32 as c::t>::f");
EXPECT_DEMANGLING("_RNvYONvC1d1sNvC1c1t1f", "<*mut d::s as c::t>::f");
}

TEST(DemangleRust, TupleLength0) {
EXPECT_DEMANGLING("_RNvYTENvC1c1t1f", "<() as c::t>::f");
}

TEST(DemangleRust, TupleLength1) {
EXPECT_DEMANGLING("_RNvYTlENvC1c1t1f", "<(i32,) as c::t>::f");
EXPECT_DEMANGLING("_RNvYTNvC1d1sENvC1c1t1f", "<(d::s,) as c::t>::f");
}

TEST(DemangleRust, TupleLength2) {
EXPECT_DEMANGLING("_RNvYTlmENvC1c1t1f", "<(i32, u32) as c::t>::f");
EXPECT_DEMANGLING("_RNvYTNvC1d1xNvC1e1yENvC1c1t1f",
"<(d::x, e::y) as c::t>::f");
}

TEST(DemangleRust, TupleLength3) {
EXPECT_DEMANGLING("_RNvYTlmnENvC1c1t1f", "<(i32, u32, i128) as c::t>::f");
EXPECT_DEMANGLING("_RNvYTNvC1d1xNvC1e1yNvC1f1zENvC1c1t1f",
"<(d::x, e::y, f::z) as c::t>::f");
}

TEST(DemangleRust, LongerTuplesAbbreviated) {
EXPECT_DEMANGLING("_RNvYTlmnoENvC1c1t1f",
"<(i32, u32, i128, ...) as c::t>::f");
EXPECT_DEMANGLING("_RNvYTlmnNvC1d1xNvC1e1yENvC1c1t1f",
"<(i32, u32, i128, ...) as c::t>::f");
}

} // namespace
} // namespace debugging_internal
Expand Down

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