https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89207
Bug ID: 89207
Summary: Symbols missing in map file with LTO
Product: gcc
Version: 8.2.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: lto
Assignee: unassigned at gcc dot gnu.org
Reporter: ilg at livius dot net
CC: marxin at gcc dot gnu.org
Target Milestone: ---
Created attachment 45607
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=45607&action=edit
The elf, the map and the listing.
After finally managing to compile some embedded projects with arm-none-eabi-gcc
and '-flto', I noticed that the map file (created with something like
'-Wl,-Map,"f4b-lto-map.map"') does not include all symbols, although the
listing file created with objcopy does, so the symbols are present in the elf
file.
I attached an archive with the elf, the map and the listing.
There are multiple symbols missing, but I noticed the problem while searching
the map for the 'Reset_Handler', located, according to the the listing, at
0x080003ac:
080003ac <Reset_Handler>:
Reset_Handler():
/Users/ilg/Desktop/eclipse-workspace-2018-12/f4b-lto-map/Debug/../system/src/cortexm/exception_handlers.c:53
{
80003ac: b508 push {r3, lr}
/Users/ilg/Desktop/eclipse-workspace-2018-12/f4b-lto-map/Debug/../system/src/cortexm/exception_handlers.c:54
_start ();
80003ae: f7ff ff79 bl 80002a4 <_start>
Then I noticed that the entire .after_vectors has only 4 symbols:
*(.after_vectors .after_vectors.*)
.after_vectors
0x0000000008000188 0x238
/var/folders/n7/kxqjc5zs4qs0nb44v1l2r2j00000gn/T//ccTOZd7j.ltrans0.ltrans.o
0x00000000080001dc UsageFault_Handler_C
0x0000000008000210 BusFault_Handler_C
0x0000000008000244 HardFault_Handler_C
0x00000000080002a4 _start
.inits 0x00000000080003c0 0x2c
0x00000000080003c0 __data_regions_array_start =
.
while in reality the listing for this memory range includes many more.
For example, the same program compiled without -flto, shows for the
.after_vectors section the following:
.after_vectors
0x0000000008000188 0x130 ./system/src/newlib/_startup.o
0x0000000008000188 _start
.after_vectors
0x00000000080002b8 0x12c
./system/src/cortexm/exception_handlers.o
0x00000000080002b8 Reset_Handler
0x00000000080002be NMI_Handler
0x00000000080002c2 HardFault_Handler
0x00000000080002d6 HardFault_Handler_C
0x0000000008000334 MemManage_Handler
0x0000000008000338 BusFault_Handler
0x000000000800034c BusFault_Handler_C
0x0000000008000380 UsageFault_Handler
0x0000000008000394 UsageFault_Handler_C
0x00000000080003c8 SVC_Handler
0x00000000080003cc DebugMon_Handler
0x00000000080003d0 PendSV_Handler
.after_vectors
0x00000000080003e4 0x4
./system/src/cmsis/vectors_stm32f407xx.o
0x00000000080003e4 DMA1_Stream3_IRQHandler
(... many more ...)
0x00000000080003e4 RTC_Alarm_IRQHandler
.inits 0x00000000080003e8 0x2c
0x00000000080003e8 __data_regions_array_start =
.
I am aware that with LTO the code is restructured, and some functions may be
inlined, thus disapearing from the symbol table, but in this case the symbols
seem to remain in the symbol table, the problem being that the map generator
ommits them in the output file.
I'm using the Arm Embedded GCC 8.2.1 toolchain on a macOS.
