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From: Bernd Edlinger <bernd.edlinger@hotmail.de>
To: "gcc@gcc.gnu.org" <gcc@gcc.gnu.org>
Subject: Re: Adding -Wshadow=local to gcc build rules
Date: Wed, 02 Oct 2019 19:10:00 -0000
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On 9/18/19 3:08 PM, Bernd Edlinger wrote:
> Hi,
>=20
> I'm currently trying to add -Wshadow=3Dlocal to the gcc build rules.
> I started with -Wshadow, but gave up that idea immediately.
>=20
> As you could expect the current code base has plenty of shadowed
> local variables.  Most are trivial to resolve, some are less trivial.
> I am not finished yet, but it is clear that it will be a rather big
> patch.
>=20
> I would like to ask you if you agree that would be a desirable step,
> in improving code quality in the gcc tree.
>=20
>=20
> Thanks
> Bernd.
>=20

Hurray!!!

The build is now working with -Wshadow=3Dlocal and I need to sort out the
changes.  I hope you are gonna like it :-)
Currently it is a 600K patch file all together.

Some parts are not trivial at all, but I hope it will pay off in more
easy to follow code in various places and less errors in new code.
Also one or two real bugs were hiding near the shadowed variable.

Most of which are of the obvious kind where, one variable is shadowed by
another one, and either the inner or the outer variable need to be
renamed from name to name1, or i to j/k, or p to q, or x to y.
Sometimes also to name2 or name3, etc.

If it is a location_t I follow common practice that loc is renamed to loc0.
I avoid renaming a parameter, unless it causes much more changes.  Also
when a renamed variable appears to be named in a comment I also update
the comment.

I tried to make the change smaller if possible, rather often the
shadowed variable is of the exact same type, and no longer used at the
place where the variable is declared again.  I consider "unsigned"
and "unsigned int" as too different to re-use the variable (or parameter).
This means I did consider the control flow and data flow around each
shadowed variable if avoiding the duplicate variable is safe.


Unless there is disagreement I will go ahead and commit trivial parts
after careful regression-testing under the obvious rule.

I did also try to build a lot of cross compilers to make sure that the
targets do not break when the warning is enabled.  But it is nevertheless
rather likely that you will see some fall-out once the warning will be
enabled. So far each target (except tilepro) needed at least a few changes.

This is the list of changed files:

M       ada/gcc-interface/decl.c
M       ada/gcc-interface/trans.c
M       asan.c
M       attribs.c
M       auto-inc-dec.c
M       bb-reorder.c
M       brig/brigfrontend/brig-basic-inst-handler.cc
M       brig/brigfrontend/brig-code-entry-handler.cc
M       brig/brigfrontend/brig-function-handler.cc
M       brig/brigfrontend/brig-util.cc
M       builtins.c
M       c/c-decl.c
M       c/c-parser.c
M       c/c-typeck.c
M       c/gimple-parser.c
M       c-family/c-ada-spec.c
M       c-family/c-common.c
M       c-family/c-cppbuiltin.c
M       c-family/c-lex.c
M       c-family/c-omp.c
M       caller-save.c
M       calls.c
M       cfg.c
M       cfgbuild.c
M       cfgcleanup.c
M       cfgexpand.c
M       cfgloopmanip.c
M       cfgrtl.c
M       cgraph.c
M       cgraph.h
M       cgraphbuild.c
M       cgraphclones.c
M       cgraphunit.c
M       combine.c
M       config/aarch64/aarch64.c
M       config/aarch64/cortex-a57-fma-steering.c
M       config/aarch64/falkor-tag-collision-avoidance.c
M       config/alpha/alpha.c
M       config/arm/arm.c
M       config/csky/csky.c
M       config/elfos.h
M       config/i386/i386-expand.c
M       config/i386/i386-features.c
M       config/i386/i386-options.c
M       config/i386/i386.c
M       config/i386/x86-tune-sched.c
M       config/ia64/ia64.c
M       config/m68k/m68k.c
M       config/m68k/m68k.md
M       config/microblaze/microblaze.c
M       config/mips/mips.c
M       config/nios2/nios2.c
M       config/pa/pa.c
M       config/pa/pa.md
M       config/rs6000/rs6000-call.c
M       config/rs6000/rs6000-logue.c
M       config/rs6000/rs6000-p8swap.c
M       config/rs6000/rs6000.c
M       config/rs6000/rs6000.md
M       config/s390/s390.c
M       config/sh/sh.c
M       config/sparc/sparc.c
M       config/xtensa/xtensa.c
M       configure
M       configure.ac
M       cp/call.c
M       cp/class.c
M       cp/constexpr.c
M       cp/constraint.cc
M       cp/cp-gimplify.c
M       cp/decl.c
M       cp/decl2.c
M       cp/error.c
M       cp/friend.c
M       cp/init.c
M       cp/method.c
M       cp/name-lookup.c
M       cp/parser.c
M       cp/pt.c
M       cp/rtti.c
M       cp/semantics.c
M       cp/typeck.c
M       cp/typeck2.c
M       cprop.c
M       cse.c
M       cselib.c
M       d/d-codegen.cc
M       d/decl.cc
M       d/dmd/doc.c
M       d/dmd/dscope.c
M       d/dmd/initsem.c
M       d/expr.cc
M       defaults.h
M       df-problems.c
M       df-scan.c
M       diagnostic-show-locus.c
M       doc/invoke.texi
M       dse.c
M       dumpfile.h
M       dwarf2cfi.c
M       dwarf2out.c
M       emit-rtl.c
M       expmed.c
M       expr.c
M       final.c
M       fold-const.c
M       fortran/arith.c
M       fortran/class.c
M       fortran/decl.c
M       fortran/dependency.c
M       fortran/expr.c
M       fortran/frontend-passes.c
M       fortran/gfortranspec.c
M       fortran/io.c
M       fortran/match.c
M       fortran/module.c
M       fortran/openmp.c
M       fortran/parse.c
M       fortran/primary.c
M       fortran/resolve.c
M       fortran/simplify.c
M       fortran/trans-array.c
M       fortran/trans-common.c
M       fortran/trans-decl.c
M       fortran/trans-expr.c
M       fortran/trans-intrinsic.c
M       fortran/trans-openmp.c
M       fortran/trans-stmt.c
M       fortran/trans-types.c
M       fortran/trans.c
M       function.c
M       fwprop.c
M       gcc.c
M       gcov.c
M       gcse.c
M       genattrtab.c
M       genautomata.c
M       genextract.c
M       gengtype.c
M       genmatch.c
M       genmodes.c
M       genrecog.c
M       gensupport.c
M       ggc-page.c
M       gimple-fold.c
M       gimple-pretty-print.c
M       gimple-ssa-isolate-paths.c
M       gimple-ssa-split-paths.c
M       gimple-ssa-sprintf.c
M       gimple-ssa-store-merging.c
M       gimple-ssa-warn-restrict.c
M       gimple-streamer-in.c
M       gimplify-me.c
M       gimplify.c
M       go/gofrontend/ast-dump.cc
M       go/gofrontend/escape.cc
M       go/gofrontend/expressions.cc
M       go/gofrontend/gogo.cc
M       go/gofrontend/parse.cc
M       go/gofrontend/statements.cc
M       go/gofrontend/types.cc
M       graphite-sese-to-poly.c
M       haifa-sched.c
M       hash-table.h
M       hsa-brig.c
M       hsa-common.c
M       hsa-gen.c
M       hsa-regalloc.c
M       ifcvt.c
M       inchash.h
M       input.c
M       ipa-comdats.c
M       ipa-cp.c
M       ipa-devirt.c
M       ipa-fnsummary.c
M       ipa-icf.c
M       ipa-predicate.c
M       ipa-prop.c
M       ipa-pure-const.c
M       ipa-reference.c
M       ipa-split.c
M       ipa-sra.c
M       ipa.c
M       ira-build.c
M       ira-color.c
M       ira-conflicts.c
M       ira-costs.c
M       ira-emit.c
M       ira-lives.c
M       ira.c
M       jit/jit-recording.c
M       lcm.c
M       loop-iv.c
M       lower-subreg.c
M       lra-constraints.c
M       lra-eliminations.c
M       lra-lives.c
M       lra-remat.c
M       lto/lto-common.c
M       lto/lto-lang.c
M       lto/lto-partition.c
M       lto/lto.c
M       lto-cgraph.c
M       lto-streamer-in.c
M       lto-streamer-out.c
M       lto-wrapper.c
M       mode-switching.c
M       modulo-sched.c
M       objc/objc-act.c
M       omp-expand.c
M       omp-general.c
M       omp-low.c
M       omp-simd-clone.c
M       optabs.c
M       opts.c
M       passes.c
M       postreload.c
M       predict.c
M       pretty-print.c
M       print-tree.c
M       profile.c
M       read-md.c
M       read-rtl-function.c
M       real.c
M       recog.c
M       ree.c
M       reg-stack.c
M       regcprop.c
M       regstat.c
M       reload.c
M       reload1.c
M       reorg.c
M       resource.c
M       rtl.h
M       rtlanal.c
M       sanopt.c
M       sched-deps.c
M       sched-rgn.c
M       sel-sched.c
M       shrink-wrap.c
M       simplify-rtx.c
M       stmt.c
M       stor-layout.c
M       store-motion.c
M       symtab.c
M       tracer.c
M       trans-mem.c
M       tree-affine.c
M       tree-call-cdce.c
M       tree-cfg.c
M       tree-complex.c
M       tree-data-ref.c
M       tree-dump.c
M       tree-eh.c
M       tree-if-conv.c
M       tree-inline.c
M       tree-into-ssa.c
M       tree-loop-distribution.c
M       tree-nested.c
M       tree-outof-ssa.c
M       tree-parloops.c
M       tree-scalar-evolution.c
M       tree-sra.c
M       tree-ssa-alias.c
M       tree-ssa-ccp.c
M       tree-ssa-coalesce.c
M       tree-ssa-dce.c
M       tree-ssa-dom.c
M       tree-ssa-dse.c
M       tree-ssa-forwprop.c
M       tree-ssa-ifcombine.c
M       tree-ssa-live.c
M       tree-ssa-loop-ch.c
M       tree-ssa-loop-im.c
M       tree-ssa-loop-ivopts.c
M       tree-ssa-loop-niter.c
M       tree-ssa-loop-unswitch.c
M       tree-ssa-math-opts.c
M       tree-ssa-operands.c
M       tree-ssa-pre.c
M       tree-ssa-reassoc.c
M       tree-ssa-sccvn.c
M       tree-ssa-scopedtables.c
M       tree-ssa-sink.c
M       tree-ssa-strlen.c
M       tree-ssa-structalias.c
M       tree-ssa-threadedge.c
M       tree-ssa-threadupdate.c
M       tree-ssa-uncprop.c
M       tree-ssa-uninit.c
M       tree-ssa.c
M       tree-switch-conversion.c
M       tree-tailcall.c
M       tree-vect-data-refs.c
M       tree-vect-generic.c
M       tree-vect-loop-manip.c
M       tree-vect-loop.c
M       tree-vect-patterns.c
M       tree-vect-slp.c
M       tree-vect-stmts.c
M       tree-vectorizer.c
M       tree.c
M       var-tracking.c
M       varasm.c
M       varpool.c
M       vr-values.c
M       vtable-verify.c
M       wide-int.cc

... I guess I will sort it out now and start
with the non-trivial patches.


Thanks
Bernd.