https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78818
Bug ID: 78818
Summary: msp430 persistent attribute is not applied correctly
in some cases
Product: gcc
Version: 6.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: awygle at gmail dot com
Target Milestone: ---
The MS430 variable attribute "persistent" places variables in a special section
.persistent so that they will not be re-initialized on reset and so that the
linker can place them in non-volatile storage. Variables with this attribute
aren't placed in this section when:
1) the variables are specified as "static" AND are not initialized or are
initialized to 0. In this case the variables are placed in the .bss section.
2) the program is compiled with the -fdata-sections optimization option. In
this case the variables are placed in either .bss.foo or .text.foo.
An example program and two compilations:
test.i:
# 1 "test.c"
# 1 "<built-in>"
# 1 "<command-line>"
# 1 "test.c"
__attribute__((persistent)) int persist = 1;
__attribute__((persistent)) int global_persist = 0;
static __attribute__((persistent)) int static_persist = 1;
static __attribute__((persistent)) int static_nopersist = 0;
void main() {
while(1);
}
Compilation without -fdata-sections:
% msp430-elf-gcc -msim -c test.i -o test.o
% msp430-elf-objdump -x --syms test.o
test.o: file format elf32-msp430
test.o
architecture: MSP430X, flags 0x00000011:
HAS_RELOC, HAS_SYMS
start address 0x00000000
Sections:
Idx Name Size VMA LMA File off Algn
0 .text 00000004 00000000 00000000 00000034 2**1
CONTENTS, ALLOC, LOAD, RELOC, READONLY, CODE
1 .data 00000000 00000000 00000000 00000038 2**0
CONTENTS, ALLOC, LOAD, DATA
2 .bss 00000002 00000000 00000000 00000038 2**1
ALLOC
3 .persistent 00000006 00000000 00000000 00000038 2**1
CONTENTS, ALLOC, LOAD, DATA
4 .comment 00000012 00000000 00000000 0000003e 2**0
CONTENTS, READONLY
5 .MSP430.attributes 00000017 00000000 00000000 00000050 2**0
CONTENTS, READONLY
SYMBOL TABLE:
00000000 l df *ABS* 00000000 test.c
00000000 l d .text 00000000 .text
00000000 l d .data 00000000 .data
00000000 l d .bss 00000000 .bss
00000000 l d .persistent 00000000 .persistent
00000004 l O .persistent 00000002 static_persist
00000000 l O .bss 00000002 static_nopersist
00000000 l d .comment 00000000 .comment
00000000 l d .MSP430.attributes 00000000 .MSP430.attributes
00000000 g O .persistent 00000002 persist
00000002 g O .persistent 00000002 global_persist
00000000 *UND* 00000000 __crt0_init_bss
00000000 g F .text 00000004 main
RELOCATION RECORDS FOR [.text]:
OFFSET TYPE VALUE
00000002 R_MSP430X_ABS16 .L2
Compilation with -fdata-sections:
% msp430-elf-gcc -msim -fdata-sections -c test.i -o test.o
% msp430-elf-objdump -x --syms test.o
test.o: file format elf32-msp430
test.o
architecture: MSP430X, flags 0x00000011:
HAS_RELOC, HAS_SYMS
start address 0x00000000
Sections:
Idx Name Size VMA LMA File off Algn
0 .text 00000004 00000000 00000000 00000034 2**1
CONTENTS, ALLOC, LOAD, RELOC, READONLY, CODE
1 .data 00000000 00000000 00000000 00000038 2**0
CONTENTS, ALLOC, LOAD, DATA
2 .bss 00000000 00000000 00000000 00000038 2**0
ALLOC
3 .data.persist 00000002 00000000 00000000 00000038 2**1
CONTENTS, ALLOC, LOAD, DATA
4 .bss.global_persist 00000002 00000000 00000000 0000003a 2**1
ALLOC
5 .data.static_persist 00000002 00000000 00000000 0000003a 2**1
CONTENTS, ALLOC, LOAD, DATA
6 .bss.static_nopersist 00000002 00000000 00000000 0000003c 2**1
ALLOC
7 .comment 00000012 00000000 00000000 0000003c 2**0
CONTENTS, READONLY
8 .MSP430.attributes 00000017 00000000 00000000 0000004e 2**0
CONTENTS, READONLY
SYMBOL TABLE:
00000000 l df *ABS* 00000000 test.c
00000000 l d .text 00000000 .text
00000000 l d .data 00000000 .data
00000000 l d .bss 00000000 .bss
00000000 l d .data.persist 00000000 .data.persist
00000000 l d .bss.global_persist 00000000 .bss.global_persist
00000000 l d .data.static_persist 00000000 .data.static_persist
00000000 l O .data.static_persist 00000002 static_persist
00000000 l d .bss.static_nopersist 00000000 .bss.static_nopersist
00000000 l O .bss.static_nopersist 00000002 static_nopersist
00000000 l d .comment 00000000 .comment
00000000 l d .MSP430.attributes 00000000 .MSP430.attributes
00000000 g O .data.persist 00000002 persist
00000000 *UND* 00000000 __crt0_movedata
00000000 g O .bss.global_persist 00000002 global_persist
00000000 *UND* 00000000 __crt0_init_bss
00000000 g F .text 00000004 main
RELOCATION RECORDS FOR [.text]:
OFFSET TYPE VALUE
00000002 R_MSP430X_ABS16 .L2
The GCC build information:
% msp430-elf-gcc -v
Using built-in specs.
COLLECT_GCC=msp430-elf-gcc
COLLECT_LTO_WRAPPER=/home/awygle/toolchain/install/bin/../libexec/gcc/msp430-elf/6.2.0/lto-wrapper
Target: msp430-elf
Configured with: ../gcc-6.2.0/configure
--prefix=/home/awygle/toolchain/toolchain_new --target=msp430-elf
--without-headers --with-newlib --enable-languages=c,c++ -v
Thread model: single
gcc version 6.2.0 (GCC)
