1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
//! Read DWARF debugging information.
//!
//! * [Example Usage](#example-usage)
//! * [API Structure](#api-structure)
//! * [Using with `FallibleIterator`](#using-with-fallibleiterator)
//!
//! ## Example Usage
//!
//! Print out all of the functions in the debuggee program:
//!
//! ```rust,no_run
//! # fn example() -> Result<(), gimli::Error> {
//! # type R = gimli::EndianSlice<'static, gimli::LittleEndian>;
//! # let get_file_section_reader = |name| -> Result<R, gimli::Error> { unimplemented!() };
//! # let get_sup_file_section_reader = |name| -> Result<R, gimli::Error> { unimplemented!() };
//! // Read the DWARF sections with whatever object loader you're using.
//! // These closures should return a `Reader` instance (e.g. `EndianSlice`).
//! let loader = |section: gimli::SectionId| { get_file_section_reader(section.name()) };
//! let sup_loader = |section: gimli::SectionId| { get_sup_file_section_reader(section.name()) };
//! let mut dwarf = gimli::Dwarf::load(loader)?;
//! dwarf.load_sup(sup_loader)?;
//!
//! // Iterate over all compilation units.
//! let mut iter = dwarf.units();
//! while let Some(header) = iter.next()? {
//!     // Parse the abbreviations and other information for this compilation unit.
//!     let unit = dwarf.unit(header)?;
//!
//!     // Iterate over all of this compilation unit's entries.
//!     let mut entries = unit.entries();
//!     while let Some((_, entry)) = entries.next_dfs()? {
//!         // If we find an entry for a function, print it.
//!         if entry.tag() == gimli::DW_TAG_subprogram {
//!             println!("Found a function: {:?}", entry);
//!         }
//!     }
//! }
//! # unreachable!()
//! # }
//! ```
//!
//! Full example programs:
//!
//!   * [A simple parser](https://github.com/gimli-rs/gimli/blob/master/crates/examples/src/bin/simple.rs)
//!
//!   * [A `dwarfdump`
//!     clone](https://github.com/gimli-rs/gimli/blob/master/crates/examples/src/bin/dwarfdump.rs)
//!
//!   * [An `addr2line` clone](https://github.com/gimli-rs/addr2line)
//!
//!   * [`ddbug`](https://github.com/gimli-rs/ddbug), a utility giving insight into
//!     code generation by making debugging information readable
//!
//!   * [`dwprod`](https://github.com/fitzgen/dwprod), a tiny utility to list the
//!     compilers used to create each compilation unit within a shared library or
//!     executable (via `DW_AT_producer`)
//!
//!   * [`dwarf-validate`](https://github.com/gimli-rs/gimli/blob/master/crates/examples/src/bin/dwarf-validate.rs),
//!     a program to validate the integrity of some DWARF and its references
//!     between sections and compilation units.
//!
//! ## API Structure
//!
//! * Basic familiarity with DWARF is assumed.
//!
//! * The [`Dwarf`](./struct.Dwarf.html) type contains the commonly used DWARF
//! sections. It has methods that simplify access to debugging data that spans
//! multiple sections. Use of this type is optional, but recommended.
//!
//! * Each section gets its own type. Consider these types the entry points to
//! the library:
//!
//!   * [`DebugAbbrev`](./struct.DebugAbbrev.html): The `.debug_abbrev` section.
//!
//!   * [`DebugAddr`](./struct.DebugAddr.html): The `.debug_addr` section.
//!
//!   * [`DebugAranges`](./struct.DebugAranges.html): The `.debug_aranges`
//!   section.
//!
//!   * [`DebugFrame`](./struct.DebugFrame.html): The `.debug_frame` section.
//!
//!   * [`DebugInfo`](./struct.DebugInfo.html): The `.debug_info` section.
//!
//!   * [`DebugLine`](./struct.DebugLine.html): The `.debug_line` section.
//!
//!   * [`DebugLineStr`](./struct.DebugLineStr.html): The `.debug_line_str` section.
//!
//!   * [`DebugLoc`](./struct.DebugLoc.html): The `.debug_loc` section.
//!
//!   * [`DebugLocLists`](./struct.DebugLocLists.html): The `.debug_loclists` section.
//!
//!   * [`DebugPubNames`](./struct.DebugPubNames.html): The `.debug_pubnames`
//!   section.
//!
//!   * [`DebugPubTypes`](./struct.DebugPubTypes.html): The `.debug_pubtypes`
//!   section.
//!
//!   * [`DebugRanges`](./struct.DebugRanges.html): The `.debug_ranges` section.
//!
//!   * [`DebugRngLists`](./struct.DebugRngLists.html): The `.debug_rnglists` section.
//!
//!   * [`DebugStr`](./struct.DebugStr.html): The `.debug_str` section.
//!
//!   * [`DebugStrOffsets`](./struct.DebugStrOffsets.html): The `.debug_str_offsets` section.
//!
//!   * [`DebugTypes`](./struct.DebugTypes.html): The `.debug_types` section.
//!
//!   * [`DebugCuIndex`](./struct.DebugCuIndex.html): The `.debug_cu_index` section.
//!
//!   * [`DebugTuIndex`](./struct.DebugTuIndex.html): The `.debug_tu_index` section.
//!
//!   * [`EhFrame`](./struct.EhFrame.html): The `.eh_frame` section.
//!
//!   * [`EhFrameHdr`](./struct.EhFrameHdr.html): The `.eh_frame_hdr` section.
//!
//! * Each section type exposes methods for accessing the debugging data encoded
//! in that section. For example, the [`DebugInfo`](./struct.DebugInfo.html)
//! struct has the [`units`](./struct.DebugInfo.html#method.units) method for
//! iterating over the compilation units defined within it.
//!
//! * Offsets into a section are strongly typed: an offset into `.debug_info` is
//! the [`DebugInfoOffset`](./struct.DebugInfoOffset.html) type. It cannot be
//! used to index into the [`DebugLine`](./struct.DebugLine.html) type because
//! `DebugLine` represents the `.debug_line` section. There are similar types
//! for offsets relative to a compilation unit rather than a section.
//!
//! ## Using with `FallibleIterator`
//!
//! The standard library's `Iterator` trait and related APIs do not play well
//! with iterators where the `next` operation is fallible. One can make the
//! `Iterator`'s associated `Item` type be a `Result<T, E>`, however the
//! provided methods cannot gracefully handle the case when an `Err` is
//! returned.
//!
//! This situation led to the
//! [`fallible-iterator`](https://crates.io/crates/fallible-iterator) crate's
//! existence. You can read more of the rationale for its existence in its
//! docs. The crate provides the helpers you have come to expect (eg `map`,
//! `filter`, etc) for iterators that can fail.
//!
//! `gimli`'s many lazy parsing iterators are a perfect match for the
//! `fallible-iterator` crate's `FallibleIterator` trait because parsing is not
//! done eagerly. Parse errors later in the input might only be discovered after
//! having iterated through many items.
//!
//! To use `gimli` iterators with `FallibleIterator`, import the crate and trait
//! into your code:
//!
//! ```
//! # #[cfg(feature = "fallible-iterator")]
//! # fn foo() {
//! // Use the `FallibleIterator` trait so its methods are in scope!
//! use fallible_iterator::FallibleIterator;
//! use gimli::{DebugAranges, EndianSlice, LittleEndian};
//!
//! fn find_sum_of_address_range_lengths(aranges: DebugAranges<EndianSlice<LittleEndian>>)
//!     -> gimli::Result<u64>
//! {
//!     // `DebugAranges::headers` returns a `FallibleIterator`!
//!     aranges.headers()
//!         // `flat_map` is provided by `FallibleIterator`!
//!         .flat_map(|header| Ok(header.entries()))
//!         // `map` is provided by `FallibleIterator`!
//!         .map(|arange| Ok(arange.length()))
//!         // `fold` is provided by `FallibleIterator`!
//!         .fold(0, |sum, len| Ok(sum + len))
//! }
//! # }
//! # fn main() {}
//! ```

use core::fmt::{self, Debug};
use core::result;
#[cfg(feature = "std")]
use std::{error, io};

use crate::common::{Register, SectionId};
use crate::constants;

mod util;
pub use util::*;

mod addr;
pub use self::addr::*;

mod cfi;
pub use self::cfi::*;

#[cfg(feature = "read")]
mod dwarf;
#[cfg(feature = "read")]
pub use self::dwarf::*;

mod endian_slice;
pub use self::endian_slice::*;

#[cfg(feature = "endian-reader")]
mod endian_reader;
#[cfg(feature = "endian-reader")]
pub use self::endian_reader::*;

mod reader;
pub use self::reader::*;

#[cfg(feature = "read")]
mod abbrev;
#[cfg(feature = "read")]
pub use self::abbrev::*;

mod aranges;
pub use self::aranges::*;

mod index;
pub use self::index::*;

#[cfg(feature = "read")]
mod line;
#[cfg(feature = "read")]
pub use self::line::*;

mod lists;

mod loclists;
pub use self::loclists::*;

#[cfg(feature = "read")]
mod lookup;

mod op;
pub use self::op::*;

#[cfg(feature = "read")]
mod pubnames;
#[cfg(feature = "read")]
pub use self::pubnames::*;

#[cfg(feature = "read")]
mod pubtypes;
#[cfg(feature = "read")]
pub use self::pubtypes::*;

mod rnglists;
pub use self::rnglists::*;

mod str;
pub use self::str::*;

/// An offset into the current compilation or type unit.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Ord, PartialOrd, Hash)]
pub struct UnitOffset<T = usize>(pub T);

#[cfg(feature = "read")]
mod unit;
#[cfg(feature = "read")]
pub use self::unit::*;

mod value;
pub use self::value::*;

/// Indicates that storage should be allocated on heap.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct StoreOnHeap;

/// `EndianBuf` has been renamed to `EndianSlice`. For ease of upgrading across
/// `gimli` versions, we export this type alias.
#[deprecated(note = "EndianBuf has been renamed to EndianSlice, use that instead.")]
pub type EndianBuf<'input, Endian> = EndianSlice<'input, Endian>;

/// An error that occurred when parsing.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum Error {
    /// An I/O error occurred while reading.
    Io,
    /// Found a PC relative pointer, but the section base is undefined.
    PcRelativePointerButSectionBaseIsUndefined,
    /// Found a `.text` relative pointer, but the `.text` base is undefined.
    TextRelativePointerButTextBaseIsUndefined,
    /// Found a data relative pointer, but the data base is undefined.
    DataRelativePointerButDataBaseIsUndefined,
    /// Found a function relative pointer in a context that does not have a
    /// function base.
    FuncRelativePointerInBadContext,
    /// Cannot parse a pointer with a `DW_EH_PE_omit` encoding.
    CannotParseOmitPointerEncoding,
    /// An error parsing an unsigned LEB128 value.
    BadUnsignedLeb128,
    /// An error parsing a signed LEB128 value.
    BadSignedLeb128,
    /// An abbreviation declared that its tag is zero, but zero is reserved for
    /// null records.
    AbbreviationTagZero,
    /// An attribute specification declared that its form is zero, but zero is
    /// reserved for null records.
    AttributeFormZero,
    /// The abbreviation's has-children byte was not one of
    /// `DW_CHILDREN_{yes,no}`.
    BadHasChildren,
    /// The specified length is impossible.
    BadLength,
    /// Found an unknown `DW_FORM_*` type.
    UnknownForm,
    /// Expected a zero, found something else.
    ExpectedZero,
    /// Found an abbreviation code that has already been used.
    DuplicateAbbreviationCode,
    /// Found a duplicate arange.
    DuplicateArange,
    /// Found an unknown reserved length value.
    UnknownReservedLength,
    /// Found an unknown DWARF version.
    UnknownVersion(u64),
    /// Found a record with an unknown abbreviation code.
    UnknownAbbreviation,
    /// Hit the end of input before it was expected.
    UnexpectedEof(ReaderOffsetId),
    /// Read a null entry before it was expected.
    UnexpectedNull,
    /// Found an unknown standard opcode.
    UnknownStandardOpcode(constants::DwLns),
    /// Found an unknown extended opcode.
    UnknownExtendedOpcode(constants::DwLne),
    /// The specified address size is not supported.
    UnsupportedAddressSize(u8),
    /// The specified offset size is not supported.
    UnsupportedOffsetSize(u8),
    /// The specified field size is not supported.
    UnsupportedFieldSize(u8),
    /// The minimum instruction length must not be zero.
    MinimumInstructionLengthZero,
    /// The maximum operations per instruction must not be zero.
    MaximumOperationsPerInstructionZero,
    /// The line range must not be zero.
    LineRangeZero,
    /// The opcode base must not be zero.
    OpcodeBaseZero,
    /// Found an invalid UTF-8 string.
    BadUtf8,
    /// Expected to find the CIE ID, but found something else.
    NotCieId,
    /// Expected to find a pointer to a CIE, but found the CIE ID instead.
    NotCiePointer,
    /// Expected to find a pointer to an FDE, but found a CIE instead.
    NotFdePointer,
    /// Invalid branch target for a DW_OP_bra or DW_OP_skip.
    BadBranchTarget(u64),
    /// DW_OP_push_object_address used but no address passed in.
    InvalidPushObjectAddress,
    /// Not enough items on the stack when evaluating an expression.
    NotEnoughStackItems,
    /// Too many iterations to compute the expression.
    TooManyIterations,
    /// An unrecognized operation was found while parsing a DWARF
    /// expression.
    InvalidExpression(constants::DwOp),
    /// An unsupported operation was found while evaluating a DWARF expression.
    UnsupportedEvaluation,
    /// The expression had a piece followed by an expression
    /// terminator without a piece.
    InvalidPiece,
    /// An expression-terminating operation was followed by something
    /// other than the end of the expression or a piece operation.
    InvalidExpressionTerminator(u64),
    /// Division or modulus by zero when evaluating an expression.
    DivisionByZero,
    /// An expression operation used mismatching types.
    TypeMismatch,
    /// An expression operation required an integral type but saw a
    /// floating point type.
    IntegralTypeRequired,
    /// An expression operation used types that are not supported.
    UnsupportedTypeOperation,
    /// The shift value in an expression must be a non-negative integer.
    InvalidShiftExpression,
    /// An unknown DW_CFA_* instruction.
    UnknownCallFrameInstruction(constants::DwCfa),
    /// The end of an address range was before the beginning.
    InvalidAddressRange,
    /// The end offset of a loc list entry was before the beginning.
    InvalidLocationAddressRange,
    /// Encountered a call frame instruction in a context in which it is not
    /// valid.
    CfiInstructionInInvalidContext,
    /// When evaluating call frame instructions, found a `DW_CFA_restore_state`
    /// stack pop instruction, but the stack was empty, and had nothing to pop.
    PopWithEmptyStack,
    /// Do not have unwind info for the given address.
    NoUnwindInfoForAddress,
    /// An offset value was larger than the maximum supported value.
    UnsupportedOffset,
    /// The given pointer encoding is either unknown or invalid.
    UnknownPointerEncoding,
    /// Did not find an entry at the given offset.
    NoEntryAtGivenOffset,
    /// The given offset is out of bounds.
    OffsetOutOfBounds,
    /// Found an unknown CFI augmentation.
    UnknownAugmentation,
    /// We do not support the given pointer encoding yet.
    UnsupportedPointerEncoding,
    /// Registers larger than `u16` are not supported.
    UnsupportedRegister(u64),
    /// The CFI program defined more register rules than we have storage for.
    TooManyRegisterRules,
    /// Attempted to push onto the CFI or evaluation stack, but it was already
    /// at full capacity.
    StackFull,
    /// The `.eh_frame_hdr` binary search table claims to be variable-length encoded,
    /// which makes binary search impossible.
    VariableLengthSearchTable,
    /// The `DW_UT_*` value for this unit is not supported yet.
    UnsupportedUnitType,
    /// Ranges using AddressIndex are not supported yet.
    UnsupportedAddressIndex,
    /// Nonzero segment selector sizes aren't supported yet.
    UnsupportedSegmentSize,
    /// A compilation unit or type unit is missing its top level DIE.
    MissingUnitDie,
    /// A DIE attribute used an unsupported form.
    UnsupportedAttributeForm,
    /// Missing DW_LNCT_path in file entry format.
    MissingFileEntryFormatPath,
    /// Expected an attribute value to be a string form.
    ExpectedStringAttributeValue,
    /// `DW_FORM_implicit_const` used in an invalid context.
    InvalidImplicitConst,
    /// Invalid section count in `.dwp` index.
    InvalidIndexSectionCount,
    /// Invalid slot count in `.dwp` index.
    InvalidIndexSlotCount,
    /// Invalid hash row in `.dwp` index.
    InvalidIndexRow,
    /// Unknown section type in `.dwp` index.
    UnknownIndexSection,
}

impl fmt::Display for Error {
    #[inline]
    fn fmt(&self, f: &mut fmt::Formatter) -> ::core::result::Result<(), fmt::Error> {
        write!(f, "{}", self.description())
    }
}

impl Error {
    /// A short description of the error.
    pub fn description(&self) -> &str {
        match *self {
            Error::Io => "An I/O error occurred while reading.",
            Error::PcRelativePointerButSectionBaseIsUndefined => {
                "Found a PC relative pointer, but the section base is undefined."
            }
            Error::TextRelativePointerButTextBaseIsUndefined => {
                "Found a `.text` relative pointer, but the `.text` base is undefined."
            }
            Error::DataRelativePointerButDataBaseIsUndefined => {
                "Found a data relative pointer, but the data base is undefined."
            }
            Error::FuncRelativePointerInBadContext => {
                "Found a function relative pointer in a context that does not have a function base."
            }
            Error::CannotParseOmitPointerEncoding => {
                "Cannot parse a pointer with a `DW_EH_PE_omit` encoding."
            }
            Error::BadUnsignedLeb128 => "An error parsing an unsigned LEB128 value",
            Error::BadSignedLeb128 => "An error parsing a signed LEB128 value",
            Error::AbbreviationTagZero => {
                "An abbreviation declared that its tag is zero,
                 but zero is reserved for null records"
            }
            Error::AttributeFormZero => {
                "An attribute specification declared that its form is zero,
                 but zero is reserved for null records"
            }
            Error::BadHasChildren => {
                "The abbreviation's has-children byte was not one of
                 `DW_CHILDREN_{yes,no}`"
            }
            Error::BadLength => "The specified length is impossible",
            Error::UnknownForm => "Found an unknown `DW_FORM_*` type",
            Error::ExpectedZero => "Expected a zero, found something else",
            Error::DuplicateAbbreviationCode => {
                "Found an abbreviation code that has already been used"
            }
            Error::DuplicateArange => "Found a duplicate arange",
            Error::UnknownReservedLength => "Found an unknown reserved length value",
            Error::UnknownVersion(_) => "Found an unknown DWARF version",
            Error::UnknownAbbreviation => "Found a record with an unknown abbreviation code",
            Error::UnexpectedEof(_) => "Hit the end of input before it was expected",
            Error::UnexpectedNull => "Read a null entry before it was expected.",
            Error::UnknownStandardOpcode(_) => "Found an unknown standard opcode",
            Error::UnknownExtendedOpcode(_) => "Found an unknown extended opcode",
            Error::UnsupportedAddressSize(_) => "The specified address size is not supported",
            Error::UnsupportedOffsetSize(_) => "The specified offset size is not supported",
            Error::UnsupportedFieldSize(_) => "The specified field size is not supported",
            Error::MinimumInstructionLengthZero => {
                "The minimum instruction length must not be zero."
            }
            Error::MaximumOperationsPerInstructionZero => {
                "The maximum operations per instruction must not be zero."
            }
            Error::LineRangeZero => "The line range must not be zero.",
            Error::OpcodeBaseZero => "The opcode base must not be zero.",
            Error::BadUtf8 => "Found an invalid UTF-8 string.",
            Error::NotCieId => "Expected to find the CIE ID, but found something else.",
            Error::NotCiePointer => "Expected to find a CIE pointer, but found the CIE ID instead.",
            Error::NotFdePointer => {
                "Expected to find an FDE pointer, but found a CIE pointer instead."
            }
            Error::BadBranchTarget(_) => "Invalid branch target in DWARF expression",
            Error::InvalidPushObjectAddress => {
                "DW_OP_push_object_address used but no object address given"
            }
            Error::NotEnoughStackItems => "Not enough items on stack when evaluating expression",
            Error::TooManyIterations => "Too many iterations to evaluate DWARF expression",
            Error::InvalidExpression(_) => "Invalid opcode in DWARF expression",
            Error::UnsupportedEvaluation => "Unsupported operation when evaluating expression",
            Error::InvalidPiece => {
                "DWARF expression has piece followed by non-piece expression at end"
            }
            Error::InvalidExpressionTerminator(_) => "Expected DW_OP_piece or DW_OP_bit_piece",
            Error::DivisionByZero => "Division or modulus by zero when evaluating expression",
            Error::TypeMismatch => "Type mismatch when evaluating expression",
            Error::IntegralTypeRequired => "Integral type expected when evaluating expression",
            Error::UnsupportedTypeOperation => {
                "An expression operation used types that are not supported"
            }
            Error::InvalidShiftExpression => {
                "The shift value in an expression must be a non-negative integer."
            }
            Error::UnknownCallFrameInstruction(_) => "An unknown DW_CFA_* instructiion",
            Error::InvalidAddressRange => {
                "The end of an address range must not be before the beginning."
            }
            Error::InvalidLocationAddressRange => {
                "The end offset of a location list entry must not be before the beginning."
            }
            Error::CfiInstructionInInvalidContext => {
                "Encountered a call frame instruction in a context in which it is not valid."
            }
            Error::PopWithEmptyStack => {
                "When evaluating call frame instructions, found a `DW_CFA_restore_state` stack pop \
                 instruction, but the stack was empty, and had nothing to pop."
            }
            Error::NoUnwindInfoForAddress => "Do not have unwind info for the given address.",
            Error::UnsupportedOffset => {
                "An offset value was larger than the maximum supported value."
            }
            Error::UnknownPointerEncoding => {
                "The given pointer encoding is either unknown or invalid."
            }
            Error::NoEntryAtGivenOffset => "Did not find an entry at the given offset.",
            Error::OffsetOutOfBounds => "The given offset is out of bounds.",
            Error::UnknownAugmentation => "Found an unknown CFI augmentation.",
            Error::UnsupportedPointerEncoding => {
                "We do not support the given pointer encoding yet."
            }
            Error::UnsupportedRegister(_) => "Registers larger than `u16` are not supported.",
            Error::TooManyRegisterRules => {
                "The CFI program defined more register rules than we have storage for."
            }
            Error::StackFull => {
                "Attempted to push onto the CFI stack, but it was already at full capacity."
            }
            Error::VariableLengthSearchTable => {
                "The `.eh_frame_hdr` binary search table claims to be variable-length encoded, \
                 which makes binary search impossible."
            }
            Error::UnsupportedUnitType => "The `DW_UT_*` value for this unit is not supported yet",
            Error::UnsupportedAddressIndex => "Ranges involving AddressIndex are not supported yet",
            Error::UnsupportedSegmentSize => "Nonzero segment size not supported yet",
            Error::MissingUnitDie => {
                "A compilation unit or type unit is missing its top level DIE."
            }
            Error::UnsupportedAttributeForm => "A DIE attribute used an unsupported form.",
            Error::MissingFileEntryFormatPath => "Missing DW_LNCT_path in file entry format.",
            Error::ExpectedStringAttributeValue => {
                "Expected an attribute value to be a string form."
            }
            Error::InvalidImplicitConst => "DW_FORM_implicit_const used in an invalid context.",
            Error::InvalidIndexSectionCount => "Invalid section count in `.dwp` index.",
            Error::InvalidIndexSlotCount => "Invalid slot count in `.dwp` index.",
            Error::InvalidIndexRow => "Invalid hash row in `.dwp` index.",
            Error::UnknownIndexSection => "Unknown section type in `.dwp` index.",
        }
    }
}

#[cfg(feature = "std")]
impl error::Error for Error {}

#[cfg(feature = "std")]
impl From<io::Error> for Error {
    fn from(_: io::Error) -> Self {
        Error::Io
    }
}

/// The result of a parse.
pub type Result<T> = result::Result<T, Error>;

/// A convenience trait for loading DWARF sections from object files.  To be
/// used like:
///
/// ```
/// use gimli::{DebugInfo, EndianSlice, LittleEndian, Reader, Section};
///
/// let buf = [0x00, 0x01, 0x02, 0x03];
/// let reader = EndianSlice::new(&buf, LittleEndian);
/// let loader = |name| -> Result<_, ()> { Ok(reader) };
///
/// let debug_info: DebugInfo<_> = Section::load(loader).unwrap();
/// ```
pub trait Section<R>: From<R> {
    /// Returns the section id for this type.
    fn id() -> SectionId;

    /// Returns the ELF section name for this type.
    fn section_name() -> &'static str {
        Self::id().name()
    }

    /// Returns the ELF section name (if any) for this type when used in a dwo
    /// file.
    fn dwo_section_name() -> Option<&'static str> {
        Self::id().dwo_name()
    }

    /// Returns the XCOFF section name (if any) for this type when used in a XCOFF
    /// file.
    fn xcoff_section_name() -> Option<&'static str> {
        Self::id().xcoff_name()
    }

    /// Try to load the section using the given loader function.
    fn load<F, E>(f: F) -> core::result::Result<Self, E>
    where
        F: FnOnce(SectionId) -> core::result::Result<R, E>,
    {
        f(Self::id()).map(From::from)
    }

    /// Returns the `Reader` for this section.
    fn reader(&self) -> &R
    where
        R: Reader;

    /// Returns the subrange of the section that is the contribution of
    /// a unit in a `.dwp` file.
    fn dwp_range(&self, offset: u32, size: u32) -> Result<Self>
    where
        R: Reader,
    {
        let mut data = self.reader().clone();
        data.skip(R::Offset::from_u32(offset))?;
        data.truncate(R::Offset::from_u32(size))?;
        Ok(data.into())
    }

    /// Returns the `Reader` for this section.
    fn lookup_offset_id(&self, id: ReaderOffsetId) -> Option<(SectionId, R::Offset)>
    where
        R: Reader,
    {
        self.reader()
            .lookup_offset_id(id)
            .map(|offset| (Self::id(), offset))
    }
}

impl Register {
    pub(crate) fn from_u64(x: u64) -> Result<Register> {
        let y = x as u16;
        if u64::from(y) == x {
            Ok(Register(y))
        } else {
            Err(Error::UnsupportedRegister(x))
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::common::Format;
    use crate::endianity::LittleEndian;
    use test_assembler::{Endian, Section};

    #[test]
    fn test_parse_initial_length_32_ok() {
        let section = Section::with_endian(Endian::Little).L32(0x7856_3412);
        let buf = section.get_contents().unwrap();

        let input = &mut EndianSlice::new(&buf, LittleEndian);
        match input.read_initial_length() {
            Ok((length, format)) => {
                assert_eq!(input.len(), 0);
                assert_eq!(format, Format::Dwarf32);
                assert_eq!(0x7856_3412, length);
            }
            otherwise => panic!("Unexpected result: {:?}", otherwise),
        }
    }

    #[test]
    fn test_parse_initial_length_64_ok() {
        let section = Section::with_endian(Endian::Little)
            // Dwarf_64_INITIAL_UNIT_LENGTH
            .L32(0xffff_ffff)
            // Actual length
            .L64(0xffde_bc9a_7856_3412);
        let buf = section.get_contents().unwrap();
        let input = &mut EndianSlice::new(&buf, LittleEndian);

        #[cfg(target_pointer_width = "64")]
        match input.read_initial_length() {
            Ok((length, format)) => {
                assert_eq!(input.len(), 0);
                assert_eq!(format, Format::Dwarf64);
                assert_eq!(0xffde_bc9a_7856_3412, length);
            }
            otherwise => panic!("Unexpected result: {:?}", otherwise),
        }

        #[cfg(target_pointer_width = "32")]
        match input.read_initial_length() {
            Err(Error::UnsupportedOffset) => {}
            otherwise => panic!("Unexpected result: {:?}", otherwise),
        };
    }

    #[test]
    fn test_parse_initial_length_unknown_reserved_value() {
        let section = Section::with_endian(Endian::Little).L32(0xffff_fffe);
        let buf = section.get_contents().unwrap();

        let input = &mut EndianSlice::new(&buf, LittleEndian);
        match input.read_initial_length() {
            Err(Error::UnknownReservedLength) => assert!(true),
            otherwise => panic!("Unexpected result: {:?}", otherwise),
        };
    }

    #[test]
    fn test_parse_initial_length_incomplete() {
        let buf = [0xff, 0xff, 0xff]; // Need at least 4 bytes.

        let input = &mut EndianSlice::new(&buf, LittleEndian);
        match input.read_initial_length() {
            Err(Error::UnexpectedEof(_)) => assert!(true),
            otherwise => panic!("Unexpected result: {:?}", otherwise),
        };
    }

    #[test]
    fn test_parse_initial_length_64_incomplete() {
        let section = Section::with_endian(Endian::Little)
            // Dwarf_64_INITIAL_UNIT_LENGTH
            .L32(0xffff_ffff)
            // Actual length is not long enough.
            .L32(0x7856_3412);
        let buf = section.get_contents().unwrap();

        let input = &mut EndianSlice::new(&buf, LittleEndian);
        match input.read_initial_length() {
            Err(Error::UnexpectedEof(_)) => assert!(true),
            otherwise => panic!("Unexpected result: {:?}", otherwise),
        };
    }

    #[test]
    fn test_parse_offset_32() {
        let section = Section::with_endian(Endian::Little).L32(0x0123_4567);
        let buf = section.get_contents().unwrap();

        let input = &mut EndianSlice::new(&buf, LittleEndian);
        match input.read_offset(Format::Dwarf32) {
            Ok(val) => {
                assert_eq!(input.len(), 0);
                assert_eq!(val, 0x0123_4567);
            }
            otherwise => panic!("Unexpected result: {:?}", otherwise),
        };
    }

    #[test]
    fn test_parse_offset_64_small() {
        let section = Section::with_endian(Endian::Little).L64(0x0123_4567);
        let buf = section.get_contents().unwrap();

        let input = &mut EndianSlice::new(&buf, LittleEndian);
        match input.read_offset(Format::Dwarf64) {
            Ok(val) => {
                assert_eq!(input.len(), 0);
                assert_eq!(val, 0x0123_4567);
            }
            otherwise => panic!("Unexpected result: {:?}", otherwise),
        };
    }

    #[test]
    #[cfg(target_pointer_width = "64")]
    fn test_parse_offset_64_large() {
        let section = Section::with_endian(Endian::Little).L64(0x0123_4567_89ab_cdef);
        let buf = section.get_contents().unwrap();

        let input = &mut EndianSlice::new(&buf, LittleEndian);
        match input.read_offset(Format::Dwarf64) {
            Ok(val) => {
                assert_eq!(input.len(), 0);
                assert_eq!(val, 0x0123_4567_89ab_cdef);
            }
            otherwise => panic!("Unexpected result: {:?}", otherwise),
        };
    }

    #[test]
    #[cfg(target_pointer_width = "32")]
    fn test_parse_offset_64_large() {
        let section = Section::with_endian(Endian::Little).L64(0x0123_4567_89ab_cdef);
        let buf = section.get_contents().unwrap();

        let input = &mut EndianSlice::new(&buf, LittleEndian);
        match input.read_offset(Format::Dwarf64) {
            Err(Error::UnsupportedOffset) => assert!(true),
            otherwise => panic!("Unexpected result: {:?}", otherwise),
        };
    }
}