Re: [PATCHES 00/31] pahole: Bug fixes and small improvements

On 29/07/2026 20:07, Arnaldo Carvalho de Melo wrote:
> Hi,
> 
> 	Here are 31 patches fixing pre-existing bugs found via coverage
> analysis, AI-assisted review (sashiko), and manual testing. No new
> features.
> 
> Critical kernel build path fix:
>   Multi-dimensional arrays (e.g. int[2][3]) were incorrectly collapsed
>   into flat arrays (int[6]) in BTF encoding. The encoder wrote only
>   the total element count; the loader read only the first dimension.
>   Both now preserve the full dimension chain using chained
>   BTF_KIND_ARRAY nodes, matching bpftool and kernel verifier format.
> 
>   Before: pahole -F btf showed int a[3][4] as int a[12]
>   After:  int a[2][3][4] encodes as three chained BTF_KIND_ARRAY nodes
>           and round-trips correctly
> 
> Bug fixes found via coverage analysis:
>   - Fix interior pointer free and missing NULL check in btf_encoder
>   - Fix missing list head initialization in type__clone_members
>   - Fix instance memory leak on 14 early returns in
>     prototype__stdio_fprintf_value
>   - Fix error path resource leaks in ctf_loader and libctf
>   - Fix early cleanup crashes in btf_encoder__new/delete
>   - Fix dangling stack pointer: allocate type_dcu via dwarf_cu__new
>   - Fix annotation failure leaks in variable and typedef creation
>   - Fix --errno typo that decrements instead of negating
>   - Fix heap buffer overflow in languages__parse realloc
>   - Fix parse_btf_features("all") being a silent no-op
>   - Fix --fixup_silly_bitfields condition check
>   - Fix data race in tag__init() decl_file string cache
>   - Fix variable shadowing in __cus__find_struct_by_name
>   - Fix phantom holes when class__find_holes ran before byte sizes
>     were cached (eliminates 36 false "BRAIN FART ALERT" on Firefox)
>   - Add elf_strptr NULL checks and fix kfunc bounds in btf_encoder
>   - Use btf_encoder__tag_type() for all type ID computations
> 
> Other improvements:
>   - Fix -Wsign-compare warnings across the codebase
>   - cmake: Update minimum required version from 3.5 to 3.10
>   - Skip inline expansions during BTF encoding (performance)
>   - Use fseek for seekable files in --prettify and --seek_bytes
>   - Guard pipe_seek() against negative offsets
>   - Fall back to GNU objcopy when llvm-objcopy is not available
>   - Add exec_objcopy() shell-injection-safe helper
>   - Skip libdw__lock when elfutils >= 0.194 is built thread-safe
>   - Replace stale FIXME/XXX comments with explanations
>   - Remove 11 dead functions found via coverage analysis
>   - Mark file-local functions as static
> 
> There are several other series that will result in way more coverage
> and regression tests and will add support for more rust DWARF tags,
> DWARF partial units that will allow us to build the kernel with most
> of the CONFIG_DEBUG_ DWARF options (DWARF5, etc), only split DWARF
> (skeletons) is left for after these series are applied.
> 
> The end result for tests/tests is this, that runs in parallel and mimics
> the 'perf test' output:
> 
> ⬢ [acme@toolbx pahole]$ ./build-and-test-cmd.sh
> <SNIP>
> Testing pahole version:
>   v1.31-215-gcd4504f549af6fe7
> 
> Verbose mode enabled - showing diagnostic information:
>   Architecture: x86_64
>   CPUs: 32
>   Memory: 60.4 GB
>   Swap: 8.0 GB
>   Parallelism: unlimited (all tests run in parallel)
>     Tip: On low-memory systems, use -j to limit parallelism (e.g., -j 4 or -j 1)
>   Test artifacts: /tmp/pahole-tests/
>   Compiler: gcc (GCC) 16.1.1 20260515 (Red Hat 16.1.1-2)
>   libc: ldd (GNU libc) 2.43
>   bpftool: bpftool v7.6.0
>   VMLINUX: not set
>   PERF_BIN: not set
>   PERF_SRC_DIR: not set
> 
>   1: dwarves_emit.c: _Atomic type compile emission.                     : Ok
>   2: _Atomic type display and --skip_emitting_atomic_typedefs.          : Ok
>   3: Auxiliary tools: pglobal, prefcnt, dtagnames.                      : Ok
>   4: Bitfield layout and data member filtering.                         : Ok
>   5: dwarf_loader coverage: bitfields, templates, enums, inlines.       : Ok
>   6: Bitfield typedef recoding (tag__recode_dwarf_bitfield).            : Ok
>   7: DW_FORM_block byte order conversion.                               : Skip
>   8: BTF arena type tag encoding for kfuncs.                            : Ok
>   9: BTF multi-dimensional array encoding and round-trip.               : Ok
>  10: BTF bitfield encoding and loading round-trip.                      : Ok
>  11: BTF VAR and DATASEC encoding for global variables.                 : Ok
>  12: BTF deduplication of array types across CUs.                       : Ok
>  13: Distilled base BTF generation.                                     : Skip
>  14: BTF encoding options.                                              : Ok
>  15: BTF encoder coverage.                                              : Ok
>  16: BTF encoder comprehensive feature coverage.                        : Ok
>  17: BTF_KIND_FWD encoding and loading round-trip.                      : Ok
>  18: BTF encoding with invalid symbol names.                            : Ok
>  21: BTF FLOAT and ENUM64 type encoding.                                : Ok
>  22: Check BTF type tag order.                                          : Ok
>  23: BTF encoder verbose logging coverage.                              : Ok
>  24: BTF encoding into ELF via pahole -J (btf_encoder__write_elf).      : Ok
>  25: BTF true_signature: clang optimized aggregate parameters (2 structs: Ok
>  26: BTF true_signature: clang optimized aggregate parameters (2 structs: Ok
>  27: BTF true_signature: clang optimized with large union parameter     : Ok
>  28: BTF true_signature: clang optimized parameters (scalar)            : Ok
>  29: BTF true_signature: clang optimized with stack parameters (9 params: Ok
>  30: BTF true_signature: clang optimized with stack parameters (non-stat: Ok
>  31: Class name list from file.                                         : Ok
>  32: CLI display and filtering options.                                 : Ok
>  33: codiff struct comparison.                                          : Ok
>  34: codiff coverage: terse, functions, verbose, multi-CU.              : Ok
>  35: codiff member change coverage.                                     : Ok
>  36: codiff multi-CU: __cus__find_cu_by_name coverage.                  : Ok
>  37: codiff --terse (-t) type change reporting.                         : Ok
>  38: Compile emission pipeline.                                         : Ok
>  39: Compilable output and type filtering.                              : Ok
>  40: Recursive container search and verbose counts.                     : Ok
>  41: Type containment and pointer search.                               : Ok
>  42: C++ advanced DWARF tag coverage.                                   : Ok
>  43: C++ cleanup: delete_tags coverage for lexblock, parameter packs.   : Ok
>  44: C++ inheritance and namespace printing.                            : Ok
>  45: C++ value parameter pack and shadow definition disambiguation.     : Ok
>  46: C++ namespace and using-declaration display.                       : Ok
>  47: C++ variadic template parameter pack handling.                     : Ok
>  48: C++ template pretty printing round-trip.                           : Ok
>  49: C++ template template parameter pretty printing round-trip.        : Ok
>  51: Class name filtering.                                              : Ok
>  52: Default BTF on a system without BTF.                               : Ok
>  53: Display format options.                                            : Ok
>  54: dwarf_loader.c edge cases: bitfield recode, inlining, call sites.  : Ok
>  55: dwarves.c core API coverage.                                       : Ok
>  56: DWZ alternate debug file type resolution.                          : Ok
>  57: Legacy atomic_ base type emission via --compile (hand-crafted DWARF: Ok
>  58: Atomic typedef emission.                                           : Ok
>  59: dwarves_emit.c / dwarves_reorganize.c coverage.                    : Ok
>  60: DW_TAG_atomic_type member handling via --compile.                  : Ok
>  61: Type emission (--compile) and atomic typedefs.                     : Ok
>  62: Enumerator search.                                                 : Ok
>  63: Expand pointers option.                                            : Ok
>  64: Type expansion and anonymous struct options.                       : Ok
>  65: Flexible arrays accounting.                                        : Ok
>  66: dwarves_fprintf.c coverage: fn-ptr members, labels, C++ types.     : Ok
>  67: Validation of GCC optimized parameters in default BTF.             : Ok
>  68: Validation of BTF encoding of true_signatures.                     : Skip (no optimizations applied.)
>  69: Compare parallel vs merged CU loading for inter-CU type references.: Ok
>  70: Multi-file loading (cus__load_files).                              : Ok
>  71: Version output.                                                    : Ok
>  72: Struct packing and reorganization.                                 : Ok
>  73: pahole coverage: sort, word_size unions, prettify bitfields.       : Ok
>  74: Format coverage: count, skip, structs, hex, contains, first_obj_onl: Ok
>  75: Header, range and seek_bytes prettify paths.                       : Ok
>  76: pahole.c scattered option paths.                                   : Ok
>  77: pdwtags DWARF tag display.                                         : Ok
>  78: Check that pfunct can print btf_decl_tags read from BTF.           : Ok
>  79: pfunct --class and --expand_types.                                 : Ok
>  80: pfunct coverage: symtab, class, expand_types, compile.             : Ok
>  81: pfunct function statistics.                                        : Ok
>  82: pglobal basic: variables, functions, static exclusion.             : Ok
>  83: prefcnt.c: reference counting coverage.                            : Ok
>  84: prettify_bitfield                                                  : Ok
>  85: Pretty printing of files using DWARF type information.             : Ok
>  86: Prototype expression parsing and prettify.                         : Ok
>  87: Cacheline boundary display with large structs.                     : Ok
>  88: Sizes and holes display.                                           : Ok
>  89: Small files coverage: elf_symtab, gobuffer, dutil, pglobal.        : Ok
>  90: Sort with multi-CU deduplication.                                  : Ok
>  91: Sort output and separator.                                         : Ok
>  92: Statistics and filtering options.                                  : Ok
>  93: Typedef chain display.                                             : Ok
>  94: Word size LP resizing.                                             : Ok
>  95: Union word_size resize and packable hex.                           : Ok
>  96: Validation of BTF encoding of functions.                           : Ok
>  50: ctracer: struct method tracing generation.                         : Ok
>  20: Split BTF encoding (vmlinux base + kernel module).                 : Ok
>  19: BTF encoding with kernel vmlinux.                                  : Ok
>  98: Parallel reproducible DWARF Loading/Serial BTF encoding.           : Ok
>  97: BTF encoding on vmlinux.                                           : Ok
> Saved timing data to .test-times (98 tests)
> 
> ⬢ [acme@toolbx pahole]$
> 
> Cheers,
> 
> - Arnaldo

Series applied, thanks!

Alan