https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99143
Bug ID: 99143
Summary: Bad section alignment on AArch64
Product: gcc
Version: 10.2.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: nyphbl8d at gmail dot com
Target Milestone: ---
aarch64-rtems6-gcc -v output:
Using built-in specs.
COLLECT_GCC=aarch64-rtems6-gcc
COLLECT_LTO_WRAPPER=/home/opticron/rtems-development/tools/libexec/gcc/aarch64-rtems6/10.2.1/lto-wrapper
Target: aarch64-rtems6
Configured with: ../gnu-mirror-gcc-949e0ad/configure
--prefix=/home/opticron/rtems-development/tools
--bindir=/home/opticron/rtems-development/tools/bin
--exec_prefix=/home/opticron/rtems-development/tools
--includedir=/home/opticron/rtems-development/tools/include
--libdir=/home/opticron/rtems-development/tools/lib
--libexecdir=/home/opticron/rtems-development/tools/libexec
--mandir=/home/opticron/rtems-development/tools/share/man
--infodir=/home/opticron/rtems-development/tools/share/info
--datadir=/home/opticron/rtems-development/tools/share --build=x86_64-linux-gnu
--host=x86_64-linux-gnu --target=aarch64-rtems6 --disable-libstdcxx-pch
--with-gnu-as --with-gnu-ld --verbose --with-newlib --disable-nls
--without-included-gettext --disable-win32-registry
--enable-version-specific-runtime-libs --disable-lto
--enable-newlib-io-c99-formats --enable-newlib-iconv
--enable-newlib-iconv-encodings=big5,cp775,cp850,cp852,cp855,cp866,euc_jp,euc_kr,euc_tw,iso_8859_1,iso_8859_10,iso_8859_11,iso_8859_13,iso_8859_14,iso_8859_15,iso_8859_2,iso_8859_3,iso_8859_4,iso_8859_5,iso_8859_6,iso_8859_7,iso_8859_8,iso_8859_9,iso_ir_111,koi8_r,koi8_ru,koi8_u,koi8_uni,ucs_2,ucs_2_internal,ucs_2be,ucs_2le,ucs_4,ucs_4_internal,ucs_4be,ucs_4le,us_ascii,utf_16,utf_16be,utf_16le,utf_8,win_1250,win_1251,win_1252,win_1253,win_1254,win_1255,win_1256,win_1257,win_1258
--enable-threads --disable-plugin --enable-libgomp --enable-languages=c,c++
Thread model: rtems
Supported LTO compression algorithms: zlib
gcc version 10.2.1 20200918 (RTEMS 6, RSB
f5fc2bfabbd18f31901ffa6fc0e5b6b47874797c-modified, Newlib 749cbcc) (GCC)
Source file test-align.c:
char i;
char j[1];
char z[0];
unsigned long ai = _Alignof(i);
unsigned long aj = _Alignof(j);
unsigned long az = _Alignof(z);
Command line:
aarch64-rtems6-gcc -O2 -S -o - test-align.c -mabi=ilp32 -fdata-sections
Compiler output:
.arch armv8-a
.file "test-align.c"
.text
.global az
.global aj
.global ai
.global z
.global j
.global i
.section .bss.i,"aw",@nobits
.type i, %object
.size i, 1
i:
.zero 1
.section .bss.j,"aw",@nobits
.align 3
.type j, %object
.size j, 1
j:
.zero 1
.section .bss.z,"aw",@nobits
.align 3
.type z, %object
.size z, 0
z:
.section .data.ai,"aw"
.align 2
.type ai, %object
.size ai, 4
ai:
.word 1
.section .data.aj,"aw"
.align 2
.type aj, %object
.size aj, 4
aj:
.word 1
.section .data.az,"aw"
.align 2
.type az, %object
.size az, 4
az:
.word 1
.ident "GCC: (GNU) 10.2.1 20200918 (RTEMS 6, RSB
f5fc2bfabbd18f31901ffa6fc0e5b6b47874797c-modified, Newlib 749cbcc)"
test-align.i from --save-temps:
# 1 "test-align.c"
# 1 "<built-in>"
# 1 "<command-line>"
# 1 "test-align.c"
char i;
char j[1];
char z[0];
unsigned long ai = _Alignof(i);
unsigned long aj = _Alignof(j);
unsigned long az = _Alignof(z);
Description:
When generating data sections for i, j, z for AArch64/ILP32 (also applies to
LP64), GCC does not align data sections to anything less than 8 bytes, even
when _Alignof() claims that the alignment of all three data elements should be
1 byte.
