Bootstrap comparison failure: gcc/rust/rust-lex.o differs

[kxxt]

Summary

I am building gcc 14.2.1+r730+gc061ad5a36ba-1 with gcc 14.2.1+r134+gab884fffe3fc-2 for Arch Linux RISC-V

A bootstrap comparison failure occurred for gcc/rust/rust-lex.o.

Build script: https://paste.rs/578r4

Build logs:

gcc-14.2.1+r730+gc061ad5a36ba-1-riscv64-prepare.log

gcc-14.2.1+r730+gc061ad5a36ba-1-riscv64-build.log

Two rust-lex.o from stage 2 and stage 3:

rust-lex.zip

Reproducer

Does the code make use of any (1.49) nightly feature ?

• Nightly

Godbolt link

No response

Actual behavior

make[3]: Entering directory '/build/gcc/src/gcc-build'
rm -f stage_current
make[3]: Leaving directory '/build/gcc/src/gcc-build'
Comparing stages 2 and 3
Bootstrap comparison failure!
gcc/rust/rust-lex.o differs
make[2]: *** [Makefile:31146: compare] Error 1
make[1]: *** [Makefile:31126: stage3-bubble] Error 2
make: *** [Makefile:31189: bootstrap] Error 2

Expected behavior

The compiler successfully bootstraps itself.

GCC Version

c061ad5a36ba0c07d3d9d82a85aebb887def759d

[powerboat9]

Does the compiler still bootstrap with rust disabled? I'd think rust-lex.o would come from rust-lex.cc, which is a C++ file, and its compilation shouldn't be affected by the rust frontend.

[kxxt]

Does the compiler still bootstrap with rust disabled? I'd think rust-lex.o would come from rust-lex.cc, which is a C++ file, and its compilation shouldn't be affected by the rust frontend.

Thanks for the suggestion! I will try a build with rust disabled.

[kxxt]

Does the compiler still bootstrap with rust disabled?

Yes. With rust disabled, it bootstraps successfully. So the problem is very specific to rust-lex.o.

build.log

I'd think rust-lex.o would come from rust-lex.cc, which is a C++ file, and its compilation shouldn't be affected by the rust frontend.

Then do you have any clue about how this could happen? Thanks!

[kxxt]

After running diffoscope, I find a very obvious difference in plain text apart from other differences:

$ readelf --wide --decompress --string-dump=.gnu.lto_.opts rust-lex.2.o 

String dump of section '.gnu.lto_.opts':
  [     0]  '-fno-openmp' '-fno-openacc' '-fcf-protection=none' '-g' '-mabi=lp64d' '-misa-spec=20191213' '-mtls-dialect=trad' '-march=rv64imafdc_zicsr_zifencei' '-O2' '-O2' '-flto=jobserver' '-frandom-seed=1' '-fasynchronous-unwind-tables' '-fno-PIE' '-fno-plt' '-fexceptions' '-fstack-clash-protection' '-fno-omit-frame-pointer' '-fno-checking' '-flto=jobserver' '-frandom-seed=1'

$ readelf --wide --decompress --string-dump=.gnu.lto_.opts rust-lex.3.o

String dump of section '.gnu.lto_.opts':
  [     0]  '-fno-openmp' '-fno-openacc' '-fcf-protection=none' '-g' '-mabi=lp64d' '-misa-spec=20191213' '-mtls-dialect=trad' '-march=rv64imafdc_zicsr_zifencei' '-O2' '-O2' '-fchecking=1' '-flto=jobserver' '-frandom-seed=1' '-fasynchronous-unwind-tables' '-fno-PIE' '-fno-plt' '-fexceptions' '-fstack-clash-protection' '-fno-omit-frame-pointer' '-fchecking=1' '-flto=jobserver' '-frandom-seed=1'

There are commandline-like strings embedded in .gnu.lto_.opts.

Stage 2 has '-fno-checking'

But Stage 3 has '-fchecking=1', which appeared twice.

And grepping through the build log, the options used to build stage 2 and 3 are indeed different:

cat ~/Downloads/gcc-14.2.1+r730+gc061ad5a36ba-1-riscv64-build.log | grep rust-lex
/build/gcc/src/gcc-build/./prev-gcc/xg++ -B/build/gcc/src/gcc-build/./prev-gcc/ -B/usr/riscv64-unknown-linux-gnu/bin/ -nostdinc++ -B/build/gcc/src/gcc-build/prev-riscv64-unknown-linux-gnu/libstdc++-v3/src/.libs -B/build/gcc/src/gcc-build/prev-riscv64-unknown-linux-gnu/libstdc++-v3/libsupc++/.libs  -I/build/gcc/src/gcc-build/prev-riscv64-unknown-linux-gnu/libstdc++-v3/include/riscv64-unknown-linux-gnu  -I/build/gcc/src/gcc-build/prev-riscv64-unknown-linux-gnu/libstdc++-v3/include  -I/build/gcc/src/gcc/libstdc++-v3/libsupc++ -L/build/gcc/src/gcc-build/prev-riscv64-unknown-linux-gnu/libstdc++-v3/src/.libs -L/build/gcc/src/gcc-build/prev-riscv64-unknown-linux-gnu/libstdc++-v3/libsupc++/.libs  -fno-PIE -c  -I /build/gcc/src/gcc/gcc/rust -I /build/gcc/src/gcc/gcc/rust/lex -I /build/gcc/src/gcc/gcc/rust/parse -I /build/gcc/src/gcc/gcc/rust/ast -I /build/gcc/src/gcc/gcc/rust/analysis -I /build/gcc/src/gcc/gcc/rust/backend -I /build/gcc/src/gcc/gcc/rust/expand -I /build/gcc/src/gcc/gcc/rust/hir/tree -I /build/gcc/src/gcc/gcc/rust/hir -I /build/gcc/src/gcc/gcc/rust/resolve -I /build/gcc/src/gcc/gcc/rust/util -I /build/gcc/src/gcc/gcc/rust/typecheck -I /build/gcc/src/gcc/gcc/rust/checks/lints -I /build/gcc/src/gcc/gcc/rust/checks/errors -I /build/gcc/src/gcc/gcc/rust/checks/errors/privacy -I /build/gcc/src/gcc/gcc/rust/checks/errors/borrowck -I /build/gcc/src/gcc/gcc/rust/util -I /build/gcc/src/gcc/gcc/rust/metadata -I /build/gcc/src/gcc/gcc/../libgrust -DIN_GCC_FRONTEND -march=rv64gc -mabi=lp64d -O2 -pipe -fno-plt -fexceptions         -Wp,-D_FORTIFY_SOURCE=3 -Wformat          -fstack-clash-protection         -fno-omit-frame-pointer -g -ffile-prefix-map=/build/gcc/src=/usr/src/debug/gcc -fno-checking -flto=jobserver -frandom-seed=1 -DIN_GCC    -fno-exceptions -fno-rtti -fasynchronous-unwind-tables -W -Wall -Wno-narrowing -Wwrite-strings -Wcast-qual -Wmissing-format-attribute -Wconditionally-supported -Woverloaded-virtual -pedantic -Wno-long-long -Wno-variadic-macros -Wno-overlength-strings -Wno-unused-parameter   -DHAVE_CONFIG_H -fno-PIE -I. -Irust -I/build/gcc/src/gcc/gcc -I/build/gcc/src/gcc/gcc/rust -I/build/gcc/src/gcc/gcc/../include  -I/build/gcc/src/gcc/gcc/../libcpp/include -I/build/gcc/src/gcc/gcc/../libcody  -I/build/gcc/src/gcc/gcc/../libdecnumber -I/build/gcc/src/gcc/gcc/../libdecnumber/dpd -I../libdecnumber -I/build/gcc/src/gcc/gcc/../libbacktrace   -o rust/rust-lex.o -MT rust/rust-lex.o -MMD -MP -MF rust/.deps/rust-lex.TPo -march=rv64gc -mabi=lp64d -O2 -pipe -fno-plt -fexceptions         -Wp,-D_FORTIFY_SOURCE=3 -Wformat          -fstack-clash-protection         -fno-omit-frame-pointer -g -ffile-prefix-map=/build/gcc/src=/usr/src/debug/gcc -fno-checking -flto=jobserver -frandom-seed=1 -I /build/gcc/src/gcc/gcc/rust -I /build/gcc/src/gcc/gcc/rust/lex -I /build/gcc/src/gcc/gcc/rust/parse -I /build/gcc/src/gcc/gcc/rust/ast -I /build/gcc/src/gcc/gcc/rust/analysis -I /build/gcc/src/gcc/gcc/rust/backend -I /build/gcc/src/gcc/gcc/rust/expand -I /build/gcc/src/gcc/gcc/rust/hir/tree -I /build/gcc/src/gcc/gcc/rust/hir -I /build/gcc/src/gcc/gcc/rust/resolve -I /build/gcc/src/gcc/gcc/rust/util -I /build/gcc/src/gcc/gcc/rust/typecheck -I /build/gcc/src/gcc/gcc/rust/checks/lints -I /build/gcc/src/gcc/gcc/rust/checks/errors -I /build/gcc/src/gcc/gcc/rust/checks/errors/privacy -I /build/gcc/src/gcc/gcc/rust/checks/errors/borrowck -I /build/gcc/src/gcc/gcc/rust/util -I /build/gcc/src/gcc/gcc/rust/metadata -I /build/gcc/src/gcc/gcc/../libgrust /build/gcc/src/gcc/gcc/rust/lex/rust-lex.cc
      rust/rust-lang.o rust/rust-attribs.o rust/rust-object-export.o rust/rust-linemap.o rust/rust-diagnostics.o rust/rust-gcc.o rust/rust-token.o rust/rust-lex.o rust/rust-cfg-parser.o rust/rust-parse.o rust/rust-ast.o rust/rust-ast-formatting.o rust/rust-path.o rust/rust-pattern.o rust/rust-ast-fragment.o rust/rust-ast-dump.o rust/rust-ast-collector.o rust/rust-ast-visitor.o rust/rust-hir-dump.o rust/rust-session-manager.o rust/rust-compile.o rust/rust-mangle.o rust/rust-mangle-v0.o rust/rust-mangle-legacy.o rust/rust-compile-resolve-path.o rust/rust-macro-expand.o rust/rust-cfg-strip.o rust/rust-expand-visitor.o rust/rust-ast-builder.o rust/rust-derive.o rust/rust-derive-clone.o rust/rust-derive-copy.o rust/rust-proc-macro.o rust/rust-macro-invoc-lexer.o rust/rust-proc-macro-invoc-lexer.o rust/rust-macro-substitute-ctx.o rust/rust-macro-builtins.o rust/rust-hir.o rust/rust-hir-map.o rust/rust-attributes.o rust/rust-keyword-values.o rust/rust-abi.o rust/rust-token-converter.o rust/rust-macro.o rust/rust-ast-lower.o rust/rust-ast-lower-base.o rust/rust-ast-lower-pattern.o rust/rust-ast-lower-item.o rust/rust-ast-lower-implitem.o rust/rust-ast-lower-expr.o rust/rust-ast-lower-type.o rust/rust-ast-lower-stmt.o rust/rust-rib.o rust/rust-name-resolution-context.o rust/rust-default-resolver.o rust/rust-toplevel-name-resolver-2.0.o rust/rust-early-name-resolver-2.0.o rust/rust-late-name-resolver-2.0.o rust/rust-early-name-resolver.o rust/rust-name-resolver.o rust/rust-ast-resolve.o rust/rust-ast-resolve-base.o rust/rust-ast-resolve-item.o rust/rust-ast-resolve-pattern.o rust/rust-ast-resolve-expr.o rust/rust-ast-resolve-type.o rust/rust-ast-resolve-path.o rust/rust-ast-resolve-stmt.o rust/rust-ast-resolve-struct-expr-field.o rust/rust-hir-type-check.o rust/rust-privacy-check.o rust/rust-privacy-ctx.o rust/rust-reachability.o rust/rust-visibility-resolver.o rust/rust-pub-restricted-visitor.o rust/rust-privacy-reporter.o rust/rust-tyty.o rust/rust-tyty-util.o rust/rust-tyty-call.o rust/rust-tyty-subst.o rust/rust-typecheck-context.o rust/rust-tyty-bounds.o rust/rust-hir-trait-resolve.o rust/rust-hir-trait-reference.o rust/rust-hir-type-check-item.o rust/rust-hir-type-check-type.o rust/rust-hir-type-check-struct.o rust/rust-hir-type-check-pattern.o rust/rust-hir-type-check-expr.o rust/rust-hir-type-check-stmt.o rust/rust-hir-type-check-enumitem.o rust/rust-hir-type-check-implitem.o rust/rust-borrow-checker.o rust/rust-bir-builder-expr-stmt.o rust/rust-bir-dump.o rust/rust-hir-dot-operator.o rust/rust-hir-path-probe.o rust/rust-type-util.o rust/rust-coercion.o rust/rust-casts.o rust/rust-unify.o rust/rust-hir-type-check-base.o rust/rust-autoderef.o rust/rust-substitution-mapper.o rust/rust-const-checker.o rust/rust-lint-marklive.o rust/rust-lint-unused-var.o rust/rust-readonly-check.o rust/rust-hir-type-check-path.o rust/rust-unsafe-checker.o rust/rust-compile-intrinsic.o rust/rust-compile-pattern.o rust/rust-compile-fnparam.o rust/rust-compile-proc-macro.o rust/rust-base62.o rust/rust-compile-item.o rust/rust-compile-implitem.o rust/rust-compile-stmt.o rust/rust-compile-expr.o rust/rust-compile-type.o rust/rust-compile-block.o rust/rust-compile-struct-field-expr.o rust/rust-constexpr.o rust/rust-compile-base.o rust/rust-tree.o rust/rust-compile-context.o rust/rust-export-metadata.o rust/rust-imports.o rust/rust-import-archive.o rust/rust-extern-crate.o rust/rust-builtins.o rust/rust-feature.o rust/rust-feature-gate.o rust/rust-ast-validation.o rust/rust-dir-owner.o rust/rust-unicode.o rust/rust-punycode.o  linux-rust.o attribs.o libbackend.a main.o libcommon-target.a libcommon.a ../libcpp/libcpp.a ../libdecnumber/libdecnumber.a libcommon.a ../libcpp/libcpp.a   ../libbacktrace/.libs/libbacktrace.a ../libiberty/libiberty.a ../libdecnumber/libdecnumber.a  ../libgrust/libproc_macro_internal/libproc_macro_internal.a -lisl -lmpc -lmpfr -lgmp -rdynamic  -lz -lzstd 
/build/gcc/src/gcc-build/./prev-gcc/xg++ -B/build/gcc/src/gcc-build/./prev-gcc/ -B/usr/riscv64-unknown-linux-gnu/bin/ -nostdinc++ -B/build/gcc/src/gcc-build/prev-riscv64-unknown-linux-gnu/libstdc++-v3/src/.libs -B/build/gcc/src/gcc-build/prev-riscv64-unknown-linux-gnu/libstdc++-v3/libsupc++/.libs  -I/build/gcc/src/gcc-build/prev-riscv64-unknown-linux-gnu/libstdc++-v3/include/riscv64-unknown-linux-gnu  -I/build/gcc/src/gcc-build/prev-riscv64-unknown-linux-gnu/libstdc++-v3/include  -I/build/gcc/src/gcc/libstdc++-v3/libsupc++ -L/build/gcc/src/gcc-build/prev-riscv64-unknown-linux-gnu/libstdc++-v3/src/.libs -L/build/gcc/src/gcc-build/prev-riscv64-unknown-linux-gnu/libstdc++-v3/libsupc++/.libs  -fno-PIE -c  -I /build/gcc/src/gcc/gcc/rust -I /build/gcc/src/gcc/gcc/rust/lex -I /build/gcc/src/gcc/gcc/rust/parse -I /build/gcc/src/gcc/gcc/rust/ast -I /build/gcc/src/gcc/gcc/rust/analysis -I /build/gcc/src/gcc/gcc/rust/backend -I /build/gcc/src/gcc/gcc/rust/expand -I /build/gcc/src/gcc/gcc/rust/hir/tree -I /build/gcc/src/gcc/gcc/rust/hir -I /build/gcc/src/gcc/gcc/rust/resolve -I /build/gcc/src/gcc/gcc/rust/util -I /build/gcc/src/gcc/gcc/rust/typecheck -I /build/gcc/src/gcc/gcc/rust/checks/lints -I /build/gcc/src/gcc/gcc/rust/checks/errors -I /build/gcc/src/gcc/gcc/rust/checks/errors/privacy -I /build/gcc/src/gcc/gcc/rust/checks/errors/borrowck -I /build/gcc/src/gcc/gcc/rust/util -I /build/gcc/src/gcc/gcc/rust/metadata -I /build/gcc/src/gcc/gcc/../libgrust -DIN_GCC_FRONTEND -march=rv64gc -mabi=lp64d -O2 -pipe -fno-plt -fexceptions         -Wp,-D_FORTIFY_SOURCE=3 -Wformat          -fstack-clash-protection         -fno-omit-frame-pointer -g -ffile-prefix-map=/build/gcc/src=/usr/src/debug/gcc -fchecking=1 -flto=jobserver -frandom-seed=1 -DIN_GCC    -fno-exceptions -fno-rtti -fasynchronous-unwind-tables -W -Wall -Wno-narrowing -Wwrite-strings -Wcast-qual -Wmissing-format-attribute -Wconditionally-supported -Woverloaded-virtual -pedantic -Wno-long-long -Wno-variadic-macros -Wno-overlength-strings -Wno-unused-parameter   -DHAVE_CONFIG_H -fno-PIE -I. -Irust -I/build/gcc/src/gcc/gcc -I/build/gcc/src/gcc/gcc/rust -I/build/gcc/src/gcc/gcc/../include  -I/build/gcc/src/gcc/gcc/../libcpp/include -I/build/gcc/src/gcc/gcc/../libcody  -I/build/gcc/src/gcc/gcc/../libdecnumber -I/build/gcc/src/gcc/gcc/../libdecnumber/dpd -I../libdecnumber -I/build/gcc/src/gcc/gcc/../libbacktrace   -o rust/rust-lex.o -MT rust/rust-lex.o -MMD -MP -MF rust/.deps/rust-lex.TPo -march=rv64gc -mabi=lp64d -O2 -pipe -fno-plt -fexceptions         -Wp,-D_FORTIFY_SOURCE=3 -Wformat          -fstack-clash-protection         -fno-omit-frame-pointer -g -ffile-prefix-map=/build/gcc/src=/usr/src/debug/gcc -fchecking=1 -flto=jobserver -frandom-seed=1 -I /build/gcc/src/gcc/gcc/rust -I /build/gcc/src/gcc/gcc/rust/lex -I /build/gcc/src/gcc/gcc/rust/parse -I /build/gcc/src/gcc/gcc/rust/ast -I /build/gcc/src/gcc/gcc/rust/analysis -I /build/gcc/src/gcc/gcc/rust/backend -I /build/gcc/src/gcc/gcc/rust/expand -I /build/gcc/src/gcc/gcc/rust/hir/tree -I /build/gcc/src/gcc/gcc/rust/hir -I /build/gcc/src/gcc/gcc/rust/resolve -I /build/gcc/src/gcc/gcc/rust/util -I /build/gcc/src/gcc/gcc/rust/typecheck -I /build/gcc/src/gcc/gcc/rust/checks/lints -I /build/gcc/src/gcc/gcc/rust/checks/errors -I /build/gcc/src/gcc/gcc/rust/checks/errors/privacy -I /build/gcc/src/gcc/gcc/rust/checks/errors/borrowck -I /build/gcc/src/gcc/gcc/rust/util -I /build/gcc/src/gcc/gcc/rust/metadata -I /build/gcc/src/gcc/gcc/../libgrust /build/gcc/src/gcc/gcc/rust/lex/rust-lex.cc
      rust/rust-lang.o rust/rust-attribs.o rust/rust-object-export.o rust/rust-linemap.o rust/rust-diagnostics.o rust/rust-gcc.o rust/rust-token.o rust/rust-lex.o rust/rust-cfg-parser.o rust/rust-parse.o rust/rust-ast.o rust/rust-ast-formatting.o rust/rust-path.o rust/rust-pattern.o rust/rust-ast-fragment.o rust/rust-ast-dump.o rust/rust-ast-collector.o rust/rust-ast-visitor.o rust/rust-hir-dump.o rust/rust-session-manager.o rust/rust-compile.o rust/rust-mangle.o rust/rust-mangle-v0.o rust/rust-mangle-legacy.o rust/rust-compile-resolve-path.o rust/rust-macro-expand.o rust/rust-cfg-strip.o rust/rust-expand-visitor.o rust/rust-ast-builder.o rust/rust-derive.o rust/rust-derive-clone.o rust/rust-derive-copy.o rust/rust-proc-macro.o rust/rust-macro-invoc-lexer.o rust/rust-proc-macro-invoc-lexer.o rust/rust-macro-substitute-ctx.o rust/rust-macro-builtins.o rust/rust-hir.o rust/rust-hir-map.o rust/rust-attributes.o rust/rust-keyword-values.o rust/rust-abi.o rust/rust-token-converter.o rust/rust-macro.o rust/rust-ast-lower.o rust/rust-ast-lower-base.o rust/rust-ast-lower-pattern.o rust/rust-ast-lower-item.o rust/rust-ast-lower-implitem.o rust/rust-ast-lower-expr.o rust/rust-ast-lower-type.o rust/rust-ast-lower-stmt.o rust/rust-rib.o rust/rust-name-resolution-context.o rust/rust-default-resolver.o rust/rust-toplevel-name-resolver-2.0.o rust/rust-early-name-resolver-2.0.o rust/rust-late-name-resolver-2.0.o rust/rust-early-name-resolver.o rust/rust-name-resolver.o rust/rust-ast-resolve.o rust/rust-ast-resolve-base.o rust/rust-ast-resolve-item.o rust/rust-ast-resolve-pattern.o rust/rust-ast-resolve-expr.o rust/rust-ast-resolve-type.o rust/rust-ast-resolve-path.o rust/rust-ast-resolve-stmt.o rust/rust-ast-resolve-struct-expr-field.o rust/rust-hir-type-check.o rust/rust-privacy-check.o rust/rust-privacy-ctx.o rust/rust-reachability.o rust/rust-visibility-resolver.o rust/rust-pub-restricted-visitor.o rust/rust-privacy-reporter.o rust/rust-tyty.o rust/rust-tyty-util.o rust/rust-tyty-call.o rust/rust-tyty-subst.o rust/rust-typecheck-context.o rust/rust-tyty-bounds.o rust/rust-hir-trait-resolve.o rust/rust-hir-trait-reference.o rust/rust-hir-type-check-item.o rust/rust-hir-type-check-type.o rust/rust-hir-type-check-struct.o rust/rust-hir-type-check-pattern.o rust/rust-hir-type-check-expr.o rust/rust-hir-type-check-stmt.o rust/rust-hir-type-check-enumitem.o rust/rust-hir-type-check-implitem.o rust/rust-borrow-checker.o rust/rust-bir-builder-expr-stmt.o rust/rust-bir-dump.o rust/rust-hir-dot-operator.o rust/rust-hir-path-probe.o rust/rust-type-util.o rust/rust-coercion.o rust/rust-casts.o rust/rust-unify.o rust/rust-hir-type-check-base.o rust/rust-autoderef.o rust/rust-substitution-mapper.o rust/rust-const-checker.o rust/rust-lint-marklive.o rust/rust-lint-unused-var.o rust/rust-readonly-check.o rust/rust-hir-type-check-path.o rust/rust-unsafe-checker.o rust/rust-compile-intrinsic.o rust/rust-compile-pattern.o rust/rust-compile-fnparam.o rust/rust-compile-proc-macro.o rust/rust-base62.o rust/rust-compile-item.o rust/rust-compile-implitem.o rust/rust-compile-stmt.o rust/rust-compile-expr.o rust/rust-compile-type.o rust/rust-compile-block.o rust/rust-compile-struct-field-expr.o rust/rust-constexpr.o rust/rust-compile-base.o rust/rust-tree.o rust/rust-compile-context.o rust/rust-export-metadata.o rust/rust-imports.o rust/rust-import-archive.o rust/rust-extern-crate.o rust/rust-builtins.o rust/rust-feature.o rust/rust-feature-gate.o rust/rust-ast-validation.o rust/rust-dir-owner.o rust/rust-unicode.o rust/rust-punycode.o  linux-rust.o attribs.o libbackend.a main.o libcommon-target.a libcommon.a ../libcpp/libcpp.a ../libdecnumber/libdecnumber.a libcommon.a ../libcpp/libcpp.a   ../libbacktrace/.libs/libbacktrace.a ../libiberty/libiberty.a ../libdecnumber/libdecnumber.a  ../libgrust/libproc_macro_internal/libproc_macro_internal.a -lisl -lmpc -lmpfr -lgmp -rdynamic  -lz -lzstd 
gcc/rust/rust-lex.o differs

[powerboat9]

https://gcc.gnu.org/onlinedocs/gcc/Developer-Options.html

While I don't know what could be causing the issue, I'm not sure that's it -- it looks like that's only supposed to affect code generation if -fchecking is set to 2

[powerboat9]

What does objdump -d show differently for each?

[kxxt]

https://gcc.gnu.org/onlinedocs/gcc/Developer-Options.html

While I don't know what could be causing the issue, I'm not sure that's it -- it looks like that's only supposed to affect code generation if -fchecking is set to 2

Yes, you are right. It appears that gcc strips the lto opts before comparing them so this difference doesn't matter. (with contrib/compare-lto)

./compare-lto  rust-lex.2.o rust-lex.3.o 
rust-lex.2.o rust-lex.3.o differ: byte 41, line 1
stripping off LTO option section, then retrying
rust-lex.2.o.stripped rust-lex.3.o.stripped differ: byte 2360617, line 2960

[kxxt]

What does objdump -d show differently for each?

From the output of diffoscope: https://repos.kxxt.dev/temp/diff.htm

The most different section is .gnu.lto_.jmpfuncs.1.
Other differences are mostly offsets.

The diff of disasm of this section is too big to read:

 diff -u <(objdump --disassemble-all --section .gnu.lto_.jmpfuncs.1  rust-lex.2.o)  <(objdump --disassemble-all --section .gnu.lto_.jmpfuncs.1  rust-lex.3.o) > diff.log

diff.log