I've tried to build stage3 with
-Wleading-whitespace=blanks -Wtrailing-whitespace=blank -Wno-error=leading-whitespace=blanks -Wno-error=trailing-whitespace=blank
added to STRICT_WARN and that expectably resulted in about
2744 unique trailing whitespace warnings and 124837 leading whitespace
warnings when excluding *.md files (which obviously is in big part a
generator issue).  Others from that are generator related, I think those
need to be solved later.

The following patch just fixes up the easy case (trailing whitespace),
which could be easily automated:
for i in `find . -name \*.h -o -name \*.cc -o -name \*.c | xargs grep -l '[ 	]$' | grep -v testsuite/`; do sed -i -e 's/[ 	]*$//' $i; done
I've excluded files which I knew are obviously generated or go FE.

Is there anything else we'd want to avoid the changes?

Due to patch size, I've split it between gcc/ part
and rest (include/, libiberty/, libgcc/, libcpp/, libstdc++-v3/;
this part).

2024-10-24  Jakub Jelinek  <jakub@redhat.com>

include/
	* dyn-string.h: Remove trailing whitespace.
	* libiberty.h: Likewise.
	* xregex.h: Likewise.
	* splay-tree.h: Likewise.
	* partition.h: Likewise.
	* plugin-api.h: Likewise.
	* demangle.h: Likewise.
	* vtv-change-permission.h: Likewise.
	* fibheap.h: Likewise.
	* hsa_ext_image.h: Likewise.
	* hashtab.h: Likewise.
	* libcollector.h: Likewise.
	* sort.h: Likewise.
	* symcat.h: Likewise.
	* hsa_ext_amd.h: Likewise.
libcpp/
	* directives.cc: Remove trailing whitespace.
	* mkdeps.cc: Likewise.
	* line-map.cc: Likewise.
	* internal.h: Likewise.
	* files.cc: Likewise.
	* init.cc: Likewise.
	* makeucnid.cc: Likewise.
	* system.h: Likewise.
	* include/line-map.h: Likewise.
	* include/symtab.h: Likewise.
	* include/cpplib.h: Likewise.
	* expr.cc: Likewise.
	* charset.cc: Likewise.
	* macro.cc: Likewise.
	* errors.cc: Likewise.
	* lex.cc: Likewise.
	* traditional.cc: Likewise.
libgcc/
	* crtstuff.c: Remove trailing whitespace.
	* libgcov.h: Likewise.
	* config/alpha/crtfastmath.c: Likewise.
	* config/alpha/vms-gcc_shell_handler.c: Likewise.
	* config/alpha/vms-unwind.h: Likewise.
	* config/pa/linux-atomic.c: Likewise.
	* config/pa/linux-unwind.h: Likewise.
	* config/pa/quadlib.c: Likewise.
	* config/pa/fptr.c: Likewise.
	* config/s390/32/_fixsfdi.c: Likewise.
	* config/s390/32/_fixunssfdi.c: Likewise.
	* config/s390/32/_fixunsdfdi.c: Likewise.
	* config/c6x/pr-support.c: Likewise.
	* config/lm32/_udivsi3.c: Likewise.
	* config/lm32/libgcc_lm32.h: Likewise.
	* config/lm32/_udivmodsi4.c: Likewise.
	* config/lm32/_mulsi3.c: Likewise.
	* config/lm32/_modsi3.c: Likewise.
	* config/lm32/_umodsi3.c: Likewise.
	* config/lm32/_divsi3.c: Likewise.
	* config/darwin-crt3.c: Likewise.
	* config/msp430/mpy.c: Likewise.
	* config/ia64/tf-signs.c: Likewise.
	* config/ia64/fde-vms.c: Likewise.
	* config/ia64/unwind-ia64.c: Likewise.
	* config/ia64/vms-unwind.h: Likewise.
	* config/ia64/sfp-exceptions.c: Likewise.
	* config/ia64/quadlib.c: Likewise.
	* config/ia64/unwind-ia64.h: Likewise.
	* config/rl78/vregs.h: Likewise.
	* config/arm/bpabi.c: Likewise.
	* config/arm/unwind-arm.c: Likewise.
	* config/arm/pr-support.c: Likewise.
	* config/arm/linux-atomic.c: Likewise.
	* config/arm/bpabi-lib.h: Likewise.
	* config/frv/frvend.c: Likewise.
	* config/frv/cmovw.c: Likewise.
	* config/frv/frvbegin.c: Likewise.
	* config/frv/cmovd.c: Likewise.
	* config/frv/cmovh.c: Likewise.
	* config/aarch64/cpuinfo.c: Likewise.
	* config/i386/crtfastmath.c: Likewise.
	* config/i386/cygming-crtend.c: Likewise.
	* config/i386/32/tf-signs.c: Likewise.
	* config/i386/crtprec.c: Likewise.
	* config/i386/sfp-exceptions.c: Likewise.
	* config/i386/w32-unwind.h: Likewise.
	* config/m32r/initfini.c: Likewise.
	* config/sparc/crtfastmath.c: Likewise.
	* config/gcn/amdgcn_veclib.h: Likewise.
	* config/nios2/linux-atomic.c: Likewise.
	* config/nios2/linux-unwind.h: Likewise.
	* config/nios2/lib2-mul.c: Likewise.
	* config/nios2/lib2-nios2.h: Likewise.
	* config/xtensa/unwind-dw2-xtensa.c: Likewise.
	* config/rs6000/darwin-fallback.c: Likewise.
	* config/rs6000/ibm-ldouble.c: Likewise.
	* config/rs6000/sfp-machine.h: Likewise.
	* config/rs6000/darwin-asm.h: Likewise.
	* config/rs6000/darwin-crt2.c: Likewise.
	* config/rs6000/aix-unwind.h: Likewise.
	* config/rs6000/sfp-exceptions.c: Likewise.
	* config/gthr-vxworks.c: Likewise.
	* config/riscv/atomic.c: Likewise.
	* config/visium/memcpy.c: Likewise.
	* config/darwin-crt-tm.c: Likewise.
	* config/stormy16/lib2funcs.c: Likewise.
	* config/arc/ieee-754/divtab-arc-sf.c: Likewise.
	* config/arc/ieee-754/divtab-arc-df.c: Likewise.
	* config/arc/initfini.c: Likewise.
	* config/sol2/gmon.c: Likewise.
	* config/microblaze/divsi3_table.c: Likewise.
	* config/m68k/fpgnulib.c: Likewise.
	* libgcov-driver.c: Likewise.
	* unwind-dw2.c: Likewise.
	* fp-bit.c: Likewise.
	* dfp-bit.h: Likewise.
	* dfp-bit.c: Likewise.
	* libgcov-driver-system.c: Likewise.
libgcc/config/libbid/
	* _le_td.c: Remove trailing whitespace.
	* bid128_compare.c: Likewise.
	* bid_div_macros.h: Likewise.
	* bid64_to_bid128.c: Likewise.
	* bid64_to_uint32.c: Likewise.
	* bid128_to_uint64.c: Likewise.
	* bid64_div.c: Likewise.
	* bid128_round_integral.c: Likewise.
	* bid_binarydecimal.c: Likewise.
	* bid128_string.c: Likewise.
	* bid_flag_operations.c: Likewise.
	* bid128_to_int64.c: Likewise.
	* _mul_sd.c: Likewise.
	* bid64_mul.c: Likewise.
	* bid128_noncomp.c: Likewise.
	* _gt_dd.c: Likewise.
	* bid64_add.c: Likewise.
	* bid64_string.c: Likewise.
	* bid_from_int.c: Likewise.
	* bid128.c: Likewise.
	* _ge_dd.c: Likewise.
	* _ne_sd.c: Likewise.
	* _dd_to_td.c: Likewise.
	* _unord_sd.c: Likewise.
	* bid64_to_uint64.c: Likewise.
	* _gt_sd.c: Likewise.
	* _sd_to_td.c: Likewise.
	* _addsub_td.c: Likewise.
	* _ne_td.c: Likewise.
	* bid_dpd.c: Likewise.
	* bid128_add.c: Likewise.
	* bid128_next.c: Likewise.
	* _lt_sd.c: Likewise.
	* bid64_next.c: Likewise.
	* bid128_mul.c: Likewise.
	* _lt_dd.c: Likewise.
	* _ge_td.c: Likewise.
	* _unord_dd.c: Likewise.
	* bid64_sqrt.c: Likewise.
	* bid_sqrt_macros.h: Likewise.
	* bid64_fma.c: Likewise.
	* _sd_to_dd.c: Likewise.
	* bid_conf.h: Likewise.
	* bid64_noncomp.c: Likewise.
	* bid_gcc_intrinsics.h: Likewise.
	* _gt_td.c: Likewise.
	* _ge_sd.c: Likewise.
	* bid128_minmax.c: Likewise.
	* bid128_quantize.c: Likewise.
	* bid32_to_bid64.c: Likewise.
	* bid_round.c: Likewise.
	* _td_to_sd.c: Likewise.
	* bid_inline_add.h: Likewise.
	* bid128_fma.c: Likewise.
	* _eq_td.c: Likewise.
	* bid32_to_bid128.c: Likewise.
	* bid64_rem.c: Likewise.
	* bid128_2_str_tables.c: Likewise.
	* _mul_dd.c: Likewise.
	* _dd_to_sd.c: Likewise.
	* bid128_div.c: Likewise.
	* _lt_td.c: Likewise.
	* bid64_compare.c: Likewise.
	* bid64_to_int32.c: Likewise.
	* _unord_td.c: Likewise.
	* bid128_rem.c: Likewise.
	* bid_internal.h: Likewise.
	* bid64_to_int64.c: Likewise.
	* _eq_dd.c: Likewise.
	* _td_to_dd.c: Likewise.
	* bid128_to_int32.c: Likewise.
	* bid128_to_uint32.c: Likewise.
	* _ne_dd.c: Likewise.
	* bid64_quantize.c: Likewise.
	* _le_dd.c: Likewise.
	* bid64_round_integral.c: Likewise.
	* _le_sd.c: Likewise.
	* bid64_minmax.c: Likewise.
libgcc/config/avr/libf7/
	* f7-renames.h: Remove trailing whitespace.
libstdc++-v3/
	* include/debug/debug.h: Remove trailing whitespace.
	* include/parallel/base.h: Likewise.
	* include/parallel/types.h: Likewise.
	* include/parallel/settings.h: Likewise.
	* include/parallel/multiseq_selection.h: Likewise.
	* include/parallel/partition.h: Likewise.
	* include/parallel/random_number.h: Likewise.
	* include/parallel/find_selectors.h: Likewise.
	* include/parallel/partial_sum.h: Likewise.
	* include/parallel/list_partition.h: Likewise.
	* include/parallel/search.h: Likewise.
	* include/parallel/algorithmfwd.h: Likewise.
	* include/parallel/random_shuffle.h: Likewise.
	* include/parallel/multiway_mergesort.h: Likewise.
	* include/parallel/sort.h: Likewise.
	* include/parallel/algobase.h: Likewise.
	* include/parallel/numericfwd.h: Likewise.
	* include/parallel/multiway_merge.h: Likewise.
	* include/parallel/losertree.h: Likewise.
	* include/bits/basic_ios.h: Likewise.
	* include/bits/stringfwd.h: Likewise.
	* include/bits/ostream_insert.h: Likewise.
	* include/bits/stl_heap.h: Likewise.
	* include/bits/unordered_map.h: Likewise.
	* include/bits/hashtable_policy.h: Likewise.
	* include/bits/stl_iterator_base_funcs.h: Likewise.
	* include/bits/valarray_before.h: Likewise.
	* include/bits/regex.h: Likewise.
	* include/bits/postypes.h: Likewise.
	* include/bits/stl_iterator.h: Likewise.
	* include/bits/localefwd.h: Likewise.
	* include/bits/stl_algo.h: Likewise.
	* include/bits/ios_base.h: Likewise.
	* include/bits/stl_function.h: Likewise.
	* include/bits/basic_string.h: Likewise.
	* include/bits/hashtable.h: Likewise.
	* include/bits/valarray_after.h: Likewise.
	* include/bits/char_traits.h: Likewise.
	* include/bits/gslice.h: Likewise.
	* include/bits/locale_facets_nonio.h: Likewise.
	* include/bits/mask_array.h: Likewise.
	* include/bits/specfun.h: Likewise.
	* include/bits/random.h: Likewise.
	* include/bits/slice_array.h: Likewise.
	* include/bits/valarray_array.h: Likewise.
	* include/tr1/float.h: Likewise.
	* include/tr1/functional_hash.h: Likewise.
	* include/tr1/math.h: Likewise.
	* include/tr1/hashtable_policy.h: Likewise.
	* include/tr1/stdio.h: Likewise.
	* include/tr1/complex.h: Likewise.
	* include/tr1/stdbool.h: Likewise.
	* include/tr1/stdarg.h: Likewise.
	* include/tr1/inttypes.h: Likewise.
	* include/tr1/fenv.h: Likewise.
	* include/tr1/stdlib.h: Likewise.
	* include/tr1/wchar.h: Likewise.
	* include/tr1/tgmath.h: Likewise.
	* include/tr1/limits.h: Likewise.
	* include/tr1/wctype.h: Likewise.
	* include/tr1/stdint.h: Likewise.
	* include/tr1/ctype.h: Likewise.
	* include/tr1/random.h: Likewise.
	* include/tr1/shared_ptr.h: Likewise.
	* include/ext/mt_allocator.h: Likewise.
	* include/ext/sso_string_base.h: Likewise.
	* include/ext/debug_allocator.h: Likewise.
	* include/ext/vstring_fwd.h: Likewise.
	* include/ext/pointer.h: Likewise.
	* include/ext/pod_char_traits.h: Likewise.
	* include/ext/malloc_allocator.h: Likewise.
	* include/ext/vstring.h: Likewise.
	* include/ext/bitmap_allocator.h: Likewise.
	* include/ext/pool_allocator.h: Likewise.
	* include/ext/type_traits.h: Likewise.
	* include/ext/ropeimpl.h: Likewise.
	* include/ext/codecvt_specializations.h: Likewise.
	* include/ext/throw_allocator.h: Likewise.
	* include/ext/extptr_allocator.h: Likewise.
	* include/ext/atomicity.h: Likewise.
	* include/ext/concurrence.h: Likewise.
	* include/c_compatibility/wchar.h: Likewise.
	* include/c_compatibility/stdint.h: Likewise.
	* include/backward/hash_fun.h: Likewise.
	* include/backward/binders.h: Likewise.
	* include/backward/hashtable.h: Likewise.
	* include/backward/auto_ptr.h: Likewise.
	* libsupc++/eh_arm.cc: Likewise.
	* libsupc++/unwind-cxx.h: Likewise.
	* libsupc++/si_class_type_info.cc: Likewise.
	* libsupc++/vec.cc: Likewise.
	* libsupc++/class_type_info.cc: Likewise.
	* libsupc++/vmi_class_type_info.cc: Likewise.
	* libsupc++/guard_error.cc: Likewise.
	* libsupc++/bad_typeid.cc: Likewise.
	* libsupc++/eh_personality.cc: Likewise.
	* libsupc++/atexit_arm.cc: Likewise.
	* libsupc++/pmem_type_info.cc: Likewise.
	* libsupc++/vterminate.cc: Likewise.
	* libsupc++/eh_terminate.cc: Likewise.
	* libsupc++/bad_cast.cc: Likewise.
	* libsupc++/exception_ptr.h: Likewise.
	* libsupc++/eh_throw.cc: Likewise.
	* libsupc++/bad_alloc.cc: Likewise.
	* libsupc++/nested_exception.cc: Likewise.
	* libsupc++/pointer_type_info.cc: Likewise.
	* libsupc++/pbase_type_info.cc: Likewise.
	* libsupc++/bad_array_new.cc: Likewise.
	* libsupc++/pure.cc: Likewise.
	* libsupc++/eh_exception.cc: Likewise.
	* libsupc++/bad_array_length.cc: Likewise.
	* libsupc++/cxxabi.h: Likewise.
	* libsupc++/guard.cc: Likewise.
	* libsupc++/eh_catch.cc: Likewise.
	* libsupc++/cxxabi_forced.h: Likewise.
	* libsupc++/tinfo.h: Likewise.