https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106706
Bug ID: 106706
Summary: Enabling LTO causes incorrect calculation in in_csum()
Product: gcc
Version: 12.1.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: lto
Assignee: unassigned at gcc dot gnu.org
Reporter: quentin at armitage dot org.uk
CC: marxin at gcc dot gnu.org
Target Milestone: ---
First of all, many apologies for not producing a small test case - I couldn't
find a simple example to demonstrate the issue.
The problem is that in_csum() (in lib/utils.c) returns an incorrect value when
the first call of in_csum() is inlined in vrrp_build_vrrp_v3() (in
keepalived/vrrp/vrrp.c). It appears then when the first call of in_csum() is
inlined, the wrong value of the addr parameter is used. This can be observed
with the following log output:
Calling in_csum, 0x10a 0x300
added 0x5629 to get 0x5629
added 0x0 to get 0x5629
added 0x903d to get 0xe666
added 0x5c2e to get 0x14294
added 0x5629 to get 0x198bd
added 0x1000 to get 0x1a8bd
Calling in_csum, 0x3331 0x265
added 0x3331 to get 0x1dbee
added 0x265 to get 0x1de53
added 0x6400 to get 0x24253
added 0x0 to get 0x24253
added 0x7f to get 0x242d2
added 0xf00 to get 0x251d2
added 0x2d15 to get 0x27ee7
added 0x2be to get 0x281a5
The two 16 bit values printed after "Calling in_csum" are the first two values
that should be included in the checksum calculation, and the values after added
are the values being added to the checksum. In the first call of in_csum
(inlined) the first two values at 0x10 and 0x300, but the first two values
output in in_csum() do not match. In the second call to in_csum() (not
inlined), it can be seen that the values match.
I have tried changing
log_message(LOG_INFO, "added 0x%x to get 0x%x", addr[-1], csum);
to
log_message(LOG_INFO, "addr %p added 0x%x to get 0x%x", addr, addr[-1], csum);
in in_csum() to see what value is being used for addr, but doing so stops the
problem occurring.
When LTO is not enabled, the equivalent to to debug output above is a follows
(and these are the correct values):
Calling in_csum, 0x10a 0x300
added 0x10a to get 0x10a
added 0x300 to get 0x40a
added 0x10a to get 0x514
added 0x100 to get 0x614
added 0x7000 to get 0x7614
added 0x1000 to get 0x8614
Calling in_csum, 0x3331 0x265
added 0x3331 to get 0xb945
added 0x265 to get 0xbbaa
added 0x6400 to get 0x11faa
added 0x0 to get 0x11faa
added 0x7f to get 0x12029
added 0xf00 to get 0x12f29
added 0x2d15 to get 0x15c3e
added 0x2be to get 0x15efc
This problem has been seen with GCC 11.2 (Ubuntu 22.04), GCC 12.1.1 (Fedora
36), GCC 11.3.1 (Fedora 34), GCC 12.1.1 (Fedora 37) and GCC 12.2.1 (Fedora 38 -
Rawhide). The problem does not occur when LTO is not enabled, nor with clang
(with or without LTO). The problem also does not occur if in_csum() has
__attribute__((noinline)).
The output below and attached files were generated on Fedora 34 using gcc
11.3.1.
The attached tar file contains the .i files and make.log, the full log of
building keepalived.
The output of gcc -v -save-temps when compiling lib/utils.c is:
Using built-in specs.
COLLECT_GCC=gcc
OFFLOAD_TARGET_NAMES=nvptx-none
OFFLOAD_TARGET_DEFAULT=1
Target: x86_64-redhat-linux
Configured with: ../configure --enable-bootstrap
--enable-languages=c,c++,fortran,objc,obj-c++,ada,go,d,lto --prefix=/usr
--mandir=/usr/share/man --infodir=/usr/share/info
--with-bugurl=http://bugzilla.redhat.com/bugzilla --enable-shared
--enable-threads=posix --enable-checking=release --enable-multilib
--with-system-zlib --enable-__cxa_atexit --disable-libunwind-exceptions
--enable-gnu-unique-object --enable-linker-build-id
--with-gcc-major-version-only --with-linker-hash-style=gnu --enable-plugin
--enable-initfini-array
--with-isl=/builddir/build/BUILD/gcc-11.3.1-20220421/obj-x86_64-redhat-linux/isl-install
--enable-offload-targets=nvptx-none --without-cuda-driver
--enable-gnu-indirect-function --enable-cet --with-tune=generic
--with-arch_32=i686 --build=x86_64-redhat-linux
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 11.3.1 20220421 (Red Hat 11.3.1-2) (GCC)
COLLECT_GCC_OPTIONS='-D' 'HAVE_CONFIG_H' '-I' '.' '-D' '_GNU_SOURCE' '-v'
'-save-temps' '-D' '_GNU_SOURCE' '-g' '-g' '-O2' '-flto=auto' '-v'
'-save-temps' '-Wall' '-Wextra' '-Wunused' '-Wstrict-prototypes'
'-Wabsolute-value' '-Waddress-of-packed-member' '-Walloca' '-Walloc-zero'
'-Warith-conversion' '-Warray-bounds=2' '-Wattribute-alias=2'
'-Wbad-function-cast' '-Wc11-c2x-compat' '-Wcast-align' '-Wcast-qual'
'-Wdate-time' '-Wdisabled-optimization' '-Wdouble-promotion'
'-Wduplicated-branches' '-Wduplicated-cond' '-Wfloat-conversion'
'-Wfloat-equal' '-Wformat-overflow=1' '-Wformat-signedness'
'-Wformat-truncation=1' '-Wframe-larger-than=5120' '-Wimplicit-fallthrough=3'
'-Winit-self' '-Winline' '-Winvalid-pch' '-Wjump-misses-init' '-Wlogical-op'
'-Wmissing-declarations' '-Wmissing-field-initializers'
'-Wmissing-include-dirs' '-Wmissing-prototypes' '-Wnested-externs'
'-Wnormalized=nfc' '-Wnull-dereference' '-Wold-style-definition'
'-Woverlength-strings' '-Wpointer-arith' '-Wredundant-decls' '-Wshadow'
'-Wshift-overflow=2' '-Wstack-protector' '-Wstrict-overflow=4'
'-Wstringop-overflow=2' '-Wstringop-truncation' '-Wsuggest-attribute=cold'
'-Wsuggest-attribute=format' '-Wsuggest-attribute=malloc'
'-Wsuggest-attribute=noreturn' '-Wsuggest-attribute=pure' '-Wsync-nand'
'-Wtrampolines' '-Wundef' '-Wuninitialized' '-Wunknown-pragmas'
'-Wunsuffixed-float-constants' '-Wunused-const-variable=2' '-Wvariadic-macros'
'-Wwrite-strings' '-fPIE' '-Wformat=1' '-Werror=format-security' '-fexceptions'
'-fstack-protector-strong' '--param=ssp-buffer-size=4' '-grecord-gcc-switches'
'-O2' '-g' '-O2' '-flto=auto' '-ffat-lto-objects' '-MT' 'utils.o' '-MD' '-MP'
'-MF' '.deps/utils.Tpo' '-c' '-o' 'utils.o' '-mtune=generic' '-march=x86-64'
/usr/libexec/gcc/x86_64-redhat-linux/11/cc1 -E -quiet -v -v -I . -MD utils.d
-MF .deps/utils.Tpo -MP -MT utils.o -D HAVE_CONFIG_H -D _GNU_SOURCE -D
_GNU_SOURCE -D_FORTIFY_SOURCE=2 utils.c -mtune=generic -march=x86-64 -Wall
-Wextra -Wunused -Wstrict-prototypes -Wabsolute-value
-Waddress-of-packed-member -Walloca -Walloc-zero -Warith-conversion
-Warray-bounds=2 -Wattribute-alias=2 -Wbad-function-cast -Wc11-c2x-compat
-Wcast-align -Wcast-qual -Wdate-time -Wdisabled-optimization -Wdouble-promotion
-Wduplicated-branches -Wduplicated-cond -Wfloat-conversion -Wfloat-equal
-Wformat-overflow=1 -Wformat-signedness -Wformat-truncation=1
-Wframe-larger-than=5120 -Wimplicit-fallthrough=3 -Winit-self -Winline
-Winvalid-pch -Wjump-misses-init -Wlogical-op -Wmissing-declarations
-Wmissing-field-initializers -Wmissing-include-dirs -Wmissing-prototypes
-Wnested-externs -Wnormalized=nfc -Wnull-dereference -Wold-style-definition
-Woverlength-strings -Wpointer-arith -Wredundant-decls -Wshadow
-Wshift-overflow=2 -Wstack-protector -Wstrict-overflow=4 -Wstringop-overflow=2
-Wstringop-truncation -Wsuggest-attribute=cold -Wsuggest-attribute=format
-Wsuggest-attribute=malloc -Wsuggest-attribute=noreturn
-Wsuggest-attribute=pure -Wsync-nand -Wtrampolines -Wundef -Wuninitialized
-Wunknown-pragmas -Wunsuffixed-float-constants -Wunused-const-variable=2
-Wvariadic-macros -Wwrite-strings -Wformat=1 -Werror=format-security -flto=auto
-fPIE -fexceptions -fstack-protector-strong -flto=auto -ffat-lto-objects -g -g
-grecord-gcc-switches -g -fworking-directory -O2 -O2 -O2 -fpch-preprocess -o
utils.i
ignoring nonexistent directory
"/usr/lib/gcc/x86_64-redhat-linux/11/include-fixed"
ignoring nonexistent directory
"/usr/lib/gcc/x86_64-redhat-linux/11/../../../../x86_64-redhat-linux/include"
#include "..." search starts here:
#include <...> search starts here:
.
/usr/lib/gcc/x86_64-redhat-linux/11/include
/usr/local/include
/usr/include
End of search list.
COLLECT_GCC_OPTIONS='-D' 'HAVE_CONFIG_H' '-I' '.' '-D' '_GNU_SOURCE' '-v'
'-save-temps' '-D' '_GNU_SOURCE' '-g' '-g' '-O2' '-flto=auto' '-v'
'-save-temps' '-Wall' '-Wextra' '-Wunused' '-Wstrict-prototypes'
'-Wabsolute-value' '-Waddress-of-packed-member' '-Walloca' '-Walloc-zero'
'-Warith-conversion' '-Warray-bounds=2' '-Wattribute-alias=2'
'-Wbad-function-cast' '-Wc11-c2x-compat' '-Wcast-align' '-Wcast-qual'
'-Wdate-time' '-Wdisabled-optimization' '-Wdouble-promotion'
'-Wduplicated-branches' '-Wduplicated-cond' '-Wfloat-conversion'
'-Wfloat-equal' '-Wformat-overflow=1' '-Wformat-signedness'
'-Wformat-truncation=1' '-Wframe-larger-than=5120' '-Wimplicit-fallthrough=3'
'-Winit-self' '-Winline' '-Winvalid-pch' '-Wjump-misses-init' '-Wlogical-op'
'-Wmissing-declarations' '-Wmissing-field-initializers'
'-Wmissing-include-dirs' '-Wmissing-prototypes' '-Wnested-externs'
'-Wnormalized=nfc' '-Wnull-dereference' '-Wold-style-definition'
'-Woverlength-strings' '-Wpointer-arith' '-Wredundant-decls' '-Wshadow'
'-Wshift-overflow=2' '-Wstack-protector' '-Wstrict-overflow=4'
'-Wstringop-overflow=2' '-Wstringop-truncation' '-Wsuggest-attribute=cold'
'-Wsuggest-attribute=format' '-Wsuggest-attribute=malloc'
'-Wsuggest-attribute=noreturn' '-Wsuggest-attribute=pure' '-Wsync-nand'
'-Wtrampolines' '-Wundef' '-Wuninitialized' '-Wunknown-pragmas'
'-Wunsuffixed-float-constants' '-Wunused-const-variable=2' '-Wvariadic-macros'
'-Wwrite-strings' '-fPIE' '-Wformat=1' '-Werror=format-security' '-fexceptions'
'-fstack-protector-strong' '--param=ssp-buffer-size=4' '-grecord-gcc-switches'
'-O2' '-g' '-O2' '-flto=auto' '-ffat-lto-objects' '-MT' 'utils.o' '-MD' '-MP'
'-MF' '.deps/utils.Tpo' '-c' '-o' 'utils.o' '-mtune=generic' '-march=x86-64'
/usr/libexec/gcc/x86_64-redhat-linux/11/cc1 -fpreprocessed utils.i -quiet
-dumpbase utils.c -dumpbase-ext .c -mtune=generic -march=x86-64 -g -g
-grecord-gcc-switches -g -O2 -O2 -O2 -Wall -Wextra -Wunused -Wstrict-prototypes
-Wabsolute-value -Waddress-of-packed-member -Walloca -Walloc-zero
-Warith-conversion -Warray-bounds=2 -Wattribute-alias=2 -Wbad-function-cast
-Wc11-c2x-compat -Wcast-align -Wcast-qual -Wdate-time -Wdisabled-optimization
-Wdouble-promotion -Wduplicated-branches -Wduplicated-cond -Wfloat-conversion
-Wfloat-equal -Wformat-overflow=1 -Wformat-signedness -Wformat-truncation=1
-Wframe-larger-than=5120 -Wimplicit-fallthrough=3 -Winit-self -Winline
-Winvalid-pch -Wjump-misses-init -Wlogical-op -Wmissing-declarations
-Wmissing-field-initializers -Wmissing-include-dirs -Wmissing-prototypes
-Wnested-externs -Wnormalized=nfc -Wnull-dereference -Wold-style-definition
-Woverlength-strings -Wpointer-arith -Wredundant-decls -Wshadow
-Wshift-overflow=2 -Wstack-protector -Wstrict-overflow=4 -Wstringop-overflow=2
-Wstringop-truncation -Wsuggest-attribute=cold -Wsuggest-attribute=format
-Wsuggest-attribute=malloc -Wsuggest-attribute=noreturn
-Wsuggest-attribute=pure -Wsync-nand -Wtrampolines -Wundef -Wuninitialized
-Wunknown-pragmas -Wunsuffixed-float-constants -Wunused-const-variable=2
-Wvariadic-macros -Wwrite-strings -Wformat=1 -Werror=format-security -version
-flto=auto -fPIE -fexceptions -fstack-protector-strong -flto=auto
-ffat-lto-objects --param=ssp-buffer-size=4 -o utils.s
GNU C17 (GCC) version 11.3.1 20220421 (Red Hat 11.3.1-2) (x86_64-redhat-linux)
compiled by GNU C version 11.3.1 20220421 (Red Hat 11.3.1-2), GMP
version 6.2.0, MPFR version 4.1.0-p13, MPC version 1.2.1, isl version
isl-0.18-GMP
GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
GNU C17 (GCC) version 11.3.1 20220421 (Red Hat 11.3.1-2) (x86_64-redhat-linux)
compiled by GNU C version 11.3.1 20220421 (Red Hat 11.3.1-2), GMP
version 6.2.0, MPFR version 4.1.0-p13, MPC version 1.2.1, isl version
isl-0.18-GMP
GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
Compiler executable checksum: 2796d05d4bc35faeaab7ddfb73cae85e
COLLECT_GCC_OPTIONS='-D' 'HAVE_CONFIG_H' '-I' '.' '-D' '_GNU_SOURCE' '-v'
'-save-temps' '-D' '_GNU_SOURCE' '-g' '-g' '-O2' '-flto=auto' '-v'
'-save-temps' '-Wall' '-Wextra' '-Wunused' '-Wstrict-prototypes'
'-Wabsolute-value' '-Waddress-of-packed-member' '-Walloca' '-Walloc-zero'
'-Warith-conversion' '-Warray-bounds=2' '-Wattribute-alias=2'
'-Wbad-function-cast' '-Wc11-c2x-compat' '-Wcast-align' '-Wcast-qual'
'-Wdate-time' '-Wdisabled-optimization' '-Wdouble-promotion'
'-Wduplicated-branches' '-Wduplicated-cond' '-Wfloat-conversion'
'-Wfloat-equal' '-Wformat-overflow=1' '-Wformat-signedness'
'-Wformat-truncation=1' '-Wframe-larger-than=5120' '-Wimplicit-fallthrough=3'
'-Winit-self' '-Winline' '-Winvalid-pch' '-Wjump-misses-init' '-Wlogical-op'
'-Wmissing-declarations' '-Wmissing-field-initializers'
'-Wmissing-include-dirs' '-Wmissing-prototypes' '-Wnested-externs'
'-Wnormalized=nfc' '-Wnull-dereference' '-Wold-style-definition'
'-Woverlength-strings' '-Wpointer-arith' '-Wredundant-decls' '-Wshadow'
'-Wshift-overflow=2' '-Wstack-protector' '-Wstrict-overflow=4'
'-Wstringop-overflow=2' '-Wstringop-truncation' '-Wsuggest-attribute=cold'
'-Wsuggest-attribute=format' '-Wsuggest-attribute=malloc'
'-Wsuggest-attribute=noreturn' '-Wsuggest-attribute=pure' '-Wsync-nand'
'-Wtrampolines' '-Wundef' '-Wuninitialized' '-Wunknown-pragmas'
'-Wunsuffixed-float-constants' '-Wunused-const-variable=2' '-Wvariadic-macros'
'-Wwrite-strings' '-fPIE' '-Wformat=1' '-Werror=format-security' '-fexceptions'
'-fstack-protector-strong' '--param=ssp-buffer-size=4' '-grecord-gcc-switches'
'-O2' '-g' '-O2' '-flto=auto' '-ffat-lto-objects' '-MT' 'utils.o' '-MD' '-MP'
'-MF' '.deps/utils.Tpo' '-c' '-o' 'utils.o' '-mtune=generic' '-march=x86-64'
as -v -v -I . --gdwarf-5 --64 -o utils.o utils.s
GNU assembler version 2.35.2 (x86_64-redhat-linux) using BFD version version
2.35.2-6.fc34
COMPILER_PATH=/usr/libexec/gcc/x86_64-redhat-linux/11/:/usr/libexec/gcc/x86_64-redhat-linux/11/:/usr/libexec/gcc/x86_64-redhat-linux/:/usr/lib/gcc/x86_64-redhat-linux/11/:/usr/lib/gcc/x86_64-redhat-linux/
LIBRARY_PATH=/usr/lib/gcc/x86_64-redhat-linux/11/:/usr/lib/gcc/x86_64-redhat-linux/11/../../../../lib64/:/lib/../lib64/:/usr/lib/../lib64/:/usr/lib/gcc/x86_64-redhat-linux/11/../../../:/lib/:/usr/lib/
COLLECT_GCC_OPTIONS='-D' 'HAVE_CONFIG_H' '-I' '.' '-D' '_GNU_SOURCE' '-v'
'-save-temps' '-D' '_GNU_SOURCE' '-g' '-g' '-O2' '-flto=auto' '-v'
'-save-temps' '-Wall' '-Wextra' '-Wunused' '-Wstrict-prototypes'
'-Wabsolute-value' '-Waddress-of-packed-member' '-Walloca' '-Walloc-zero'
'-Warith-conversion' '-Warray-bounds=2' '-Wattribute-alias=2'
'-Wbad-function-cast' '-Wc11-c2x-compat' '-Wcast-align' '-Wcast-qual'
'-Wdate-time' '-Wdisabled-optimization' '-Wdouble-promotion'
'-Wduplicated-branches' '-Wduplicated-cond' '-Wfloat-conversion'
'-Wfloat-equal' '-Wformat-overflow=1' '-Wformat-signedness'
'-Wformat-truncation=1' '-Wframe-larger-than=5120' '-Wimplicit-fallthrough=3'
'-Winit-self' '-Winline' '-Winvalid-pch' '-Wjump-misses-init' '-Wlogical-op'
'-Wmissing-declarations' '-Wmissing-field-initializers'
'-Wmissing-include-dirs' '-Wmissing-prototypes' '-Wnested-externs'
'-Wnormalized=nfc' '-Wnull-dereference' '-Wold-style-definition'
'-Woverlength-strings' '-Wpointer-arith' '-Wredundant-decls' '-Wshadow'
'-Wshift-overflow=2' '-Wstack-protector' '-Wstrict-overflow=4'
'-Wstringop-overflow=2' '-Wstringop-truncation' '-Wsuggest-attribute=cold'
'-Wsuggest-attribute=format' '-Wsuggest-attribute=malloc'
'-Wsuggest-attribute=noreturn' '-Wsuggest-attribute=pure' '-Wsync-nand'
'-Wtrampolines' '-Wundef' '-Wuninitialized' '-Wunknown-pragmas'
'-Wunsuffixed-float-constants' '-Wunused-const-variable=2' '-Wvariadic-macros'
'-Wwrite-strings' '-fPIE' '-Wformat=1' '-Werror=format-security' '-fexceptions'
'-fstack-protector-strong' '--param=ssp-buffer-size=4' '-grecord-gcc-switches'
'-O2' '-g' '-O2' '-flto=auto' '-ffat-lto-objects' '-MT' 'utils.o' '-MD' '-MP'
'-MF' '.deps/utils.Tpo' '-c' '-o' 'utils.o' '-mtune=generic' '-march=x86-64'
'-dumpdir' 'utils.'
