// Copyright 2024 The Abseil Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#include "absl/debugging/internal/demangle_rust.h"
#include <cstddef>
#include <cstdint>
#include <cstring>
#include <limits>
#include "absl/base/attributes.h"
#include "absl/base/config.h"
namespace absl {
ABSL_NAMESPACE_BEGIN
namespace debugging_internal {
namespace {
// Same step limit as the C++ demangler in demangle.cc uses.
constexpr int kMaxReturns = 1 << 17;
bool IsDigit(char c) { return '0' <= c && c <= '9'; }
bool IsLower(char c) { return 'a' <= c && c <= 'z'; }
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 == '_'; }
bool IsLowerHexDigit(char c) { return IsDigit(c) || ('a' <= c && c <= 'f'); }
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
class RustSymbolParser {
public:
// Prepares to demangle the given encoding, a Rust symbol name starting with
// _R, into the output buffer [out, out_end). The caller is expected to
// continue by calling the new object's Parse function.
RustSymbolParser(const char* encoding, char* out, char* const out_end)
: encoding_(encoding), out_(out), out_end_(out_end) {
if (out_ != out_end_) *out_ = '\0';
}
// Parses the constructor's encoding argument, writing output into the range
// [out, out_end). Returns true on success and false for input whose
// structure was not recognized or exceeded implementation limits, such as by
// nesting structures too deep. In either case *this should not be used
// again.
ABSL_MUST_USE_RESULT bool Parse() && {
// Recursively parses the grammar production named by callee, then resumes
// execution at the next statement.
//
// Recursive-descent parsing is a beautifully readable translation of a
// grammar, but it risks stack overflow if implemented by naive recursion on
// the C++ call stack. So we simulate recursion by goto and switch instead,
// keeping a bounded stack of "return addresses" in the recursion_stack_
// member.
//
// The callee argument is a statement label. We goto that label after
// saving the "return address" on recursion_stack_. The next continue
// statement in the for loop below "returns" from this "call".
//
// The caller argument names the return point. Each value of caller must
// appear in only one ABSL_DEMANGLER_RECURSE call and be listed in the
// definition of enum ReturnAddress. The switch implements the control
// transfer from the end of a "called" subroutine back to the statement
// after the "call".
//
// Note that not all the grammar productions have to be packed into the
// switch, but only those which appear in a cycle in the grammar. Anything
// acyclic can be written as ordinary functions and function calls, e.g.,
// ParseIdentifier.
#define ABSL_DEMANGLER_RECURSE(callee, caller) \
do { \
if (recursion_depth_ == kStackSize) return false; \
/* The next continue will switch on this saved value ... */ \
recursion_stack_[recursion_depth_++] = caller; \
goto callee; \
/* ... and will land here, resuming the suspended code. */ \
case caller: {} \
} while (0)
// Parse the encoding, counting completed recursive calls to guard against
// excessively complex input and infinite-loop bugs.
int iter = 0;
goto whole_encoding;
for (; iter < kMaxReturns && recursion_depth_ > 0; ++iter) {
// This switch resumes the code path most recently suspended by
// ABSL_DEMANGLER_RECURSE.
switch (recursion_stack_[--recursion_depth_]) {
//
// symbol-name ->
// _R decimal-number? path instantiating-crate? vendor-specific-suffix?
whole_encoding:
if (!Eat('_') || !Eat('R')) return false;
// decimal-number? is always empty today, so proceed to path, which
// can't start with a decimal digit.
ABSL_DEMANGLER_RECURSE(path, kInstantiatingCrate);
if (IsAlpha(Peek())) {
++silence_depth_; // Print nothing more from here on.
ABSL_DEMANGLER_RECURSE(path, kVendorSpecificSuffix);
}
switch (Take()) {
case '.': case '$': case '\0': return true;
}
return false; // unexpected trailing content
// 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': goto inherent_impl;
case 'X': goto trait_impl;
case 'Y': goto trait_definition;
case 'N': goto nested_path;
case 'I': goto generic_args;
case 'B': goto path_backref;
default: return false;
}
// crate-root -> C identifier (C consumed above)
crate_root:
if (!ParseIdentifier()) return false;
continue;
// inherent-impl -> M impl-path type (M already consumed)
inherent_impl:
if (!Emit("<")) return false;
ABSL_DEMANGLER_RECURSE(impl_path, kInherentImplType);
ABSL_DEMANGLER_RECURSE(type, kInherentImplEnding);
if (!Emit(">")) return false;
continue;
// trait-impl -> X impl-path type path (X already consumed)
trait_impl:
if (!Emit("<")) return false;
ABSL_DEMANGLER_RECURSE(impl_path, kTraitImplType);
ABSL_DEMANGLER_RECURSE(type, kTraitImplInfix);
if (!Emit(" as ")) return false;
ABSL_DEMANGLER_RECURSE(path, kTraitImplEnding);
if (!Emit(">")) return false;
continue;
// impl-path -> disambiguator? path (but never print it!)
impl_path:
++silence_depth_;
{
int ignored_disambiguator;
if (!ParseDisambiguator(ignored_disambiguator)) return false;
}
ABSL_DEMANGLER_RECURSE(path, kImplPathEnding);
--silence_depth_;
continue;
// 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 a stack so we can print
// ::{closure#0} or ::{shim:vtable#0} or ::{X:name#0} as needed.
if (IsUpper(Peek())) {
if (!PushNamespace(Take())) return false;
ABSL_DEMANGLER_RECURSE(path, kIdentifierInUppercaseNamespace);
if (!Emit("::")) return false;
if (!ParseIdentifier(PopNamespace())) return false;
continue;
}
// Lowercase namespaces, however, are never represented in the output;
// they all emit just ::name.
if (IsLower(Take())) {
ABSL_DEMANGLER_RECURSE(path, kIdentifierInLowercaseNamespace);
if (!Emit("::")) return false;
if (!ParseIdentifier()) return false;
continue;
}
// 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')) {
// array-type = A type const
if (!Emit("[")) return false;
ABSL_DEMANGLER_RECURSE(type, kArraySize);
if (!Emit("; ")) return false;
ABSL_DEMANGLER_RECURSE(constant, kFinishArray);
if (!Emit("]")) return false;
continue;
}
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 (!ParseOptionalLifetime()) return false;
goto type;
}
if (Eat('Q')) {
if (!Emit("&mut ")) return false;
if (!ParseOptionalLifetime()) return false;
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')) goto fn_type;
if (Eat('D')) goto dyn_trait_type;
if (Eat('B')) goto type_backref;
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;
// fn-type -> F fn-sig (F already consumed)
// fn-sig -> binder? U? (K abi)? type* E type
// abi -> C | undisambiguated-identifier
//
// We follow the C++ demangler in suppressing details of function
// signatures. Every function type is rendered "fn...".
fn_type:
if (!Emit("fn...")) return false;
++silence_depth_;
if (!ParseOptionalBinder()) return false;
(void)Eat('U');
if (Eat('K')) {
if (!Eat('C') && !ParseUndisambiguatedIdentifier()) return false;
}
while (!Eat('E')) {
ABSL_DEMANGLER_RECURSE(type, kContinueParameterList);
}
ABSL_DEMANGLER_RECURSE(type, kFinishFn);
--silence_depth_;
continue;
// dyn-trait-type -> D dyn-bounds lifetime (D already consumed)
// dyn-bounds -> binder? dyn-trait* E
//
// The grammar strangely allows an empty trait list, even though the
// compiler should never output one. We follow existing demanglers in
// rendering DEL_ as "dyn ".
//
// Because auto traits lengthen a type name considerably without
// providing much value to a search for related source code, it would be
// desirable to abbreviate
// dyn main::Trait + std::marker::Copy + std::marker::Send
// to
// dyn main::Trait + ...,
// eliding the auto traits. But it is difficult to do so correctly, in
// part because there is no guarantee that the mangling will list the
// main trait first. So we just print all the traits in their order of
// appearance in the mangled name.
dyn_trait_type:
if (!Emit("dyn ")) return false;
if (!ParseOptionalBinder()) return false;
if (!Eat('E')) {
ABSL_DEMANGLER_RECURSE(dyn_trait, kBeginAutoTraits);
while (!Eat('E')) {
if (!Emit(" + ")) return false;
ABSL_DEMANGLER_RECURSE(dyn_trait, kContinueAutoTraits);
}
}
if (!ParseRequiredLifetime()) return false;
continue;
// dyn-trait -> path dyn-trait-assoc-binding*
// dyn-trait-assoc-binding -> p undisambiguated-identifier type
//
// We render nonempty binding lists as <>, omitting their contents as
// for generic-args.
dyn_trait:
ABSL_DEMANGLER_RECURSE(path, kContinueDynTrait);
if (Peek() == 'p') {
if (!Emit("<>")) return false;
++silence_depth_;
while (Eat('p')) {
if (!ParseUndisambiguatedIdentifier()) return false;
ABSL_DEMANGLER_RECURSE(type, kContinueAssocBinding);
}
--silence_depth_;
}
continue;
// const -> type const-data | p | backref
//
// const is a C++ keyword, so we use the label `constant` instead.
constant:
if (Eat('B')) goto const_backref;
if (Eat('p')) {
if (!Emit("_")) return false;
continue;
}
// Scan the type without printing it.
//
// The Rust language restricts the type of a const generic argument
// much more than the mangling grammar does. We do not enforce this.
//
// We also do not bother printing false, true, 'A', and '\u{abcd}' for
// the types bool and char. Because we do not print generic-args
// contents, we expect to print constants only in array sizes, and
// those should not be bool or char.
++silence_depth_;
ABSL_DEMANGLER_RECURSE(type, kConstData);
--silence_depth_;
// const-data -> n? hex-digit* _
//
// Although the grammar doesn't say this, existing demanglers expect
// that zero is 0, not an empty digit sequence, and no nonzero value
// may have leading zero digits. Also n0_ is accepted and printed as
// -0, though a toolchain will probably never write that encoding.
if (Eat('n') && !EmitChar('-')) return false;
if (!Emit("0x")) return false;
if (Eat('0')) {
if (!EmitChar('0')) return false;
if (!Eat('_')) return false;
continue;
}
while (IsLowerHexDigit(Peek())) {
if (!EmitChar(Take())) return false;
}
if (!Eat('_')) return false;
continue;
// generic-args -> I path generic-arg* E (I already consumed)
//
// We follow the C++ demangler in omitting all the arguments from the
// output, printing only the list opening and closing tokens.
generic_args:
ABSL_DEMANGLER_RECURSE(path, kBeginGenericArgList);
if (!Emit("::<>")) return false;
++silence_depth_;
while (!Eat('E')) {
ABSL_DEMANGLER_RECURSE(generic_arg, kContinueGenericArgList);
}
--silence_depth_;
continue;
// generic-arg -> lifetime | type | K const
generic_arg:
if (Peek() == 'L') {
if (!ParseOptionalLifetime()) return false;
continue;
}
if (Eat('K')) goto constant;
goto type;
// backref -> B base-62-number (B already consumed)
//
// The BeginBackref call parses and range-checks the base-62-number. We
// always do that much.
//
// The recursive call parses and prints what the backref points at. We
// save CPU and stack by skipping this work if the output would be
// suppressed anyway.
path_backref:
if (!BeginBackref()) return false;
if (silence_depth_ == 0) {
ABSL_DEMANGLER_RECURSE(path, kPathBackrefEnding);
}
EndBackref();
continue;
// This represents the same backref production as in path_backref but
// parses the target as a type instead of a path.
type_backref:
if (!BeginBackref()) return false;
if (silence_depth_ == 0) {
ABSL_DEMANGLER_RECURSE(type, kTypeBackrefEnding);
}
EndBackref();
continue;
const_backref:
if (!BeginBackref()) return false;
if (silence_depth_ == 0) {
ABSL_DEMANGLER_RECURSE(constant, kConstantBackrefEnding);
}
EndBackref();
continue;
}
}
return false; // hit iteration limit or a bug in our stack handling
}
private:
// Enumerates resumption points for ABSL_DEMANGLER_RECURSE calls.
enum ReturnAddress : std::uint8_t {
kInstantiatingCrate,
kVendorSpecificSuffix,
kIdentifierInUppercaseNamespace,
kIdentifierInLowercaseNamespace,
kInherentImplType,
kInherentImplEnding,
kTraitImplType,
kTraitImplInfix,
kTraitImplEnding,
kImplPathEnding,
kTraitDefinitionInfix,
kTraitDefinitionEnding,
kArraySize,
kFinishArray,
kSliceEnding,
kAfterFirstTupleElement,
kAfterSecondTupleElement,
kAfterThirdTupleElement,
kAfterSubsequentTupleElement,
kContinueParameterList,
kFinishFn,
kBeginAutoTraits,
kContinueAutoTraits,
kContinueDynTrait,
kContinueAssocBinding,
kConstData,
kBeginGenericArgList,
kContinueGenericArgList,
kPathBackrefEnding,
kTypeBackrefEnding,
kConstantBackrefEnding,
};
// Element counts for the stack arrays. Larger stack sizes accommodate more
// deeply nested names at the cost of a larger footprint on the C++ call
// stack.
enum {
// Maximum recursive calls outstanding at one time.
kStackSize = 256,
// Maximum N<uppercase> nested-paths open at once. We do not expect
// closures inside closures inside closures as much as functions inside
// modules inside other modules, so we can use a smaller array here.
kNamespaceStackSize = 64,
// Maximum number of nested backrefs. We can keep this stack pretty small
// because we do not follow backrefs inside generic-args or other contexts
// that suppress printing, so deep stacking is unlikely in practice.
kPositionStackSize = 16,
};
// Returns the next input character without consuming it.
char Peek() const { return encoding_[pos_]; }
// Consumes and returns the next input character.
char Take() { return encoding_[pos_++]; }
// If the next input character is the given character, consumes it and returns
// true; otherwise returns false without consuming a character.
ABSL_MUST_USE_RESULT bool Eat(char want) {
if (encoding_[pos_] != want) return false;
++pos_;
return true;
}
// Provided there is enough remaining output space, appends c to the output,
// writing a fresh NUL terminator afterward, and returns true. Returns false
// if the output buffer had less than two bytes free.
ABSL_MUST_USE_RESULT bool EmitChar(char c) {
if (silence_depth_ > 0) return true;
if (out_end_ - out_ < 2) return false;
*out_++ = c;
*out_ = '\0';
return true;
}
// Provided there is enough remaining output space, appends the C string token
// to the output, followed by a NUL character, and returns true. Returns
// false if not everything fit into the output buffer.
ABSL_MUST_USE_RESULT bool Emit(const char* token) {
if (silence_depth_ > 0) return true;
const std::size_t token_length = std::strlen(token);
const std::size_t bytes_to_copy = token_length + 1; // token and final NUL
if (static_cast<std::size_t>(out_end_ - out_) < bytes_to_copy) return false;
std::memcpy(out_, token, bytes_to_copy);
out_ += token_length;
return true;
}
// Provided there is enough remaining output space, appends the decimal form
// of disambiguator (if it's nonnegative) or "?" (if it's negative) to the
// output, followed by a NUL character, and returns true. Returns false if
// not everything fit into the output buffer.
ABSL_MUST_USE_RESULT bool EmitDisambiguator(int disambiguator) {
if (disambiguator < 0) return EmitChar('?'); // parsed but too large
if (disambiguator == 0) return EmitChar('0');
// Convert disambiguator to decimal text. Three digits per byte is enough
// because 999 > 256. The bound will remain correct even if future
// maintenance changes the type of the disambiguator variable.
char digits[3 * sizeof(disambiguator)] = {};
std::size_t leading_digit_index = sizeof(digits) - 1;
for (; disambiguator > 0; disambiguator /= 10) {
digits[--leading_digit_index] =
static_cast<char>('0' + disambiguator % 10);
}
return Emit(digits + leading_digit_index);
}
// Consumes an optional disambiguator (s123_) from the input.
//
// On success returns true and fills value with the encoded value if it was
// not too big, otherwise with -1. If the optional disambiguator was omitted,
// value is 0. On parse failure returns false and sets value to -1.
ABSL_MUST_USE_RESULT bool ParseDisambiguator(int& value) {
value = -1;
// disambiguator = s base-62-number
//
// Disambiguators are optional. An omitted disambiguator is zero.
if (!Eat('s')) {
value = 0;
return true;
}
int base_62_value = 0;
if (!ParseBase62Number(base_62_value)) return false;
value = base_62_value < 0 ? -1 : base_62_value + 1;
return true;
}
// Consumes a base-62 number like _ or 123_ from the input.
//
// On success returns true and fills value with the encoded value if it was
// not too big, otherwise with -1. On parse failure returns false and sets
// value to -1.
ABSL_MUST_USE_RESULT bool ParseBase62Number(int& value) {
value = -1;
// base-62-number = (digit | lower | upper)* _
//
// An empty base-62 digit sequence means 0.
if (Eat('_')) {
value = 0;
return true;
}
// A nonempty digit sequence denotes its base-62 value plus 1.
int encoded_number = 0;
bool overflowed = false;
while (IsAlpha(Peek()) || IsDigit(Peek())) {
const char c = Take();
if (encoded_number >= std::numeric_limits<int>::max()/62) {
// If we are close to overflowing an int, keep parsing but stop updating
// encoded_number and remember to return -1 at the end. The point is to
// avoid undefined behavior while parsing crate-root disambiguators,
// which are large in practice but not shown in demangling, while
// successfully computing closure and shim disambiguators, which are
// typically small and are printed out.
overflowed = true;
} else {
int digit;
if (IsDigit(c)) {
digit = c - '0';
} else if (IsLower(c)) {
digit = c - 'a' + 10;
} else {
digit = c - 'A' + 36;
}
encoded_number = 62 * encoded_number + digit;
}
}
if (!Eat('_')) return false;
if (!overflowed) value = encoded_number + 1;
return true;
}
// Consumes an identifier from the input, returning true on success.
//
// A nonzero uppercase_namespace specifies the character after the N in a
// nested-identifier, e.g., 'C' for a closure, allowing ParseIdentifier to
// write out the name with the conventional decoration for that namespace.
ABSL_MUST_USE_RESULT bool ParseIdentifier(char uppercase_namespace = '\0') {
// identifier -> disambiguator? undisambiguated-identifier
int disambiguator = 0;
if (!ParseDisambiguator(disambiguator)) return false;
return ParseUndisambiguatedIdentifier(uppercase_namespace, disambiguator);
}
// Consumes from the input an identifier with no preceding disambiguator,
// returning true on success.
//
// When ParseIdentifier calls this, it passes the N<namespace> character and
// disambiguator value so that "{closure#42}" and similar forms can be
// rendered correctly.
//
// At other appearances of undisambiguated-identifier in the grammar, this
// treatment is not applicable, and the call site omits both arguments.
ABSL_MUST_USE_RESULT bool ParseUndisambiguatedIdentifier(
char uppercase_namespace = '\0', int disambiguator = 0) {
// undisambiguated-identifier -> u? decimal-number _? bytes
const bool is_punycoded = Eat('u');
if (!IsDigit(Peek())) return false;
int num_bytes = 0;
if (!ParseDecimalNumber(num_bytes)) return false;
(void)Eat('_'); // optional separator, needed if a digit follows
// 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) {
case 'C':
if (!Emit("{closure")) return false;
break;
case 'S':
if (!Emit("{shim")) return false;
break;
default:
if (!EmitChar('{') || !EmitChar(uppercase_namespace)) return false;
break;
}
if (num_bytes > 0 && !Emit(":")) return false;
}
// Emit the name itself.
for (int i = 0; i < num_bytes; ++i) {
const char c = Take();
if (!IsIdentifierChar(c) &&
// The spec gives toolchains the choice of Punycode or raw UTF-8 for
// identifiers containing code points above 0x7f, so accept bytes with
// the high bit set if this is not a u... encoding.
(is_punycoded || (c & 0x80) == 0)) {
return false;
}
if (!EmitChar(c)) return false;
}
// Emit the endings of braced forms: "#42}" or "}".
if (uppercase_namespace != '\0') {
if (!EmitChar('#')) return false;
if (!EmitDisambiguator(disambiguator)) return false;
}
if (uppercase_namespace != '\0' || is_punycoded) {
if (!EmitChar('}')) return false;
}
return true;
}
// Consumes a decimal number like 0 or 123 from the input. On success returns
// true and fills value with the encoded value. If the encoded value is too
// large or otherwise unparsable, returns false and sets value to -1.
ABSL_MUST_USE_RESULT bool ParseDecimalNumber(int& value) {
value = -1;
if (!IsDigit(Peek())) return false;
int encoded_number = Take() - '0';
if (encoded_number == 0) {
// Decimal numbers are never encoded with extra leading zeroes.
value = 0;
return true;
}
while (IsDigit(Peek()) &&
// avoid overflow
encoded_number < std::numeric_limits<int>::max()/10) {
encoded_number = 10 * encoded_number + (Take() - '0');
}
if (IsDigit(Peek())) return false; // too big
value = encoded_number;
return true;
}
// Consumes a binder of higher-ranked lifetimes if one is present. On success
// returns true and discards the encoded lifetime count. On parse failure
// returns false.
ABSL_MUST_USE_RESULT bool ParseOptionalBinder() {
// binder -> G base-62-number
if (!Eat('G')) return true;
int ignored_binding_count;
return ParseBase62Number(ignored_binding_count);
}
// Consumes a lifetime if one is present.
//
// On success returns true and discards the lifetime index. We do not print
// or even range-check lifetimes because they are a finer detail than other
// things we omit from output, such as the entire contents of generic-args.
//
// On parse failure returns false.
ABSL_MUST_USE_RESULT bool ParseOptionalLifetime() {
// lifetime -> L base-62-number
if (!Eat('L')) return true;
int ignored_de_bruijn_index;
return ParseBase62Number(ignored_de_bruijn_index);
}
// Consumes a lifetime just like ParseOptionalLifetime, but returns false if
// there is no lifetime here.
ABSL_MUST_USE_RESULT bool ParseRequiredLifetime() {
if (Peek() != 'L') return false;
return ParseOptionalLifetime();
}
// Pushes ns onto the namespace stack and returns true if the stack is not
// full, else returns false.
ABSL_MUST_USE_RESULT bool PushNamespace(char ns) {
if (namespace_depth_ == kNamespaceStackSize) return false;
namespace_stack_[namespace_depth_++] = ns;
return true;
}
// Pops the last pushed namespace. Requires that the namespace stack is not
// empty (namespace_depth_ > 0).
char PopNamespace() { return namespace_stack_[--namespace_depth_]; }
// Pushes position onto the position stack and returns true if the stack is
// not full, else returns false.
ABSL_MUST_USE_RESULT bool PushPosition(int position) {
if (position_depth_ == kPositionStackSize) return false;
position_stack_[position_depth_++] = position;
return true;
}
// Pops the last pushed input position. Requires that the position stack is
// not empty (position_depth_ > 0).
int PopPosition() { return position_stack_[--position_depth_]; }
// Consumes a base-62-number denoting a backref target, pushes the current
// input position on the data stack, and sets the input position to the
// beginning of the backref target. Returns true on success. Returns false
// if parsing failed, the stack is exhausted, or the backref target position
// is out of range.
ABSL_MUST_USE_RESULT bool BeginBackref() {
// backref = B base-62-number (B already consumed)
//
// Reject backrefs that don't parse, overflow int, or don't point backward.
// If the offset looks fine, adjust it to account for the _R prefix.
int offset = 0;
const int offset_of_this_backref =
pos_ - 2 /* _R */ - 1 /* B already consumed */;
if (!ParseBase62Number(offset) || offset < 0 ||
offset >= offset_of_this_backref) {
return false;
}
offset += 2;
// Save the old position to restore later.
if (!PushPosition(pos_)) return false;
// Move the input position to the backref target.
//
// Note that we do not check whether the new position points to the
// beginning of a construct matching the context in which the backref
// appeared. We just jump to it and see whether nested parsing succeeds.
// We therefore accept various wrong manglings, e.g., a type backref
// pointing to an 'l' character inside an identifier, which happens to mean
// i32 when parsed as a type mangling. This saves the complexity and RAM
// footprint of remembering which offsets began which kinds of
// substructures. Existing demanglers take similar shortcuts.
pos_ = offset;
return true;
}
// Cleans up after a backref production by restoring the previous input
// position from the data stack.
void EndBackref() { pos_ = PopPosition(); }
// The leftmost recursion_depth_ elements of recursion_stack_ contain the
// ReturnAddresses pushed by ABSL_DEMANGLER_RECURSE calls not yet completed.
ReturnAddress recursion_stack_[kStackSize] = {};
int recursion_depth_ = 0;
// The leftmost namespace_depth_ elements of namespace_stack_ contain the
// uppercase namespace identifiers for open nested-paths, e.g., 'C' for a
// closure.
char namespace_stack_[kNamespaceStackSize] = {};
int namespace_depth_ = 0;
// The leftmost position_depth_ elements of position_stack_ contain the input
// positions to return to after fully printing the targets of backrefs.
int position_stack_[kPositionStackSize] = {};
int position_depth_ = 0;
// Anything parsed while silence_depth_ > 0 contributes nothing to the
// demangled output. For constructs omitted from the demangling, such as
// impl-path and the contents of generic-args, we will increment
// silence_depth_ on the way in and decrement silence_depth_ on the way out.
int silence_depth_ = 0;
// Input: encoding_ points to a Rust mangled symbol, and encoding_[pos_] is
// the next input character to be scanned.
int pos_ = 0;
const char* encoding_ = nullptr;
// Output: *out_ is where the next output character should be written, and
// out_end_ points past the last byte of available space.
char* out_ = nullptr;
char* out_end_ = nullptr;
};
} // namespace
bool DemangleRustSymbolEncoding(const char* mangled, char* out,
std::size_t out_size) {
return RustSymbolParser(mangled, out, out + out_size).Parse();
}
} // namespace debugging_internal
ABSL_NAMESPACE_END
} // namespace absl