arm-none-eabi-nm: some symbols are not related to any source file

In my embedded project I compile `amazon-freertos/lib/FreeRTOS-Plus-TCP/FreeRTOS_Sockets.c` in this way:

/opt/gcc-arm-none-eabi-8-2019-q3-update/bin/arm-none-eabi-gcc \
	-std=gnu11 \
	-mcpu=cortex-m7 \
	-mthumb \
	-mapcs \
	-mfloat-abi=hard \
	-mfpu=fpv5-d16 \
	-fno-common \
	-fno-math-errno \
	-fsingle-precision-constant \
	-fno-trapping-math \
	-fno-signaling-nans \
	-fno-builtin \
	-fstrict-aliasing \
	-fstack-usage \
	-Wstack-usage=300 \
	-DCPU_MIMXRT1051DVL6B  \
	-D__FREERTOS__=1 \
	-DFSL_RTOS_FREE_RTOS \
	-DFSL_FEATURE_PHYKSZ8081_USE_RMII50M_MODE \
	-D__MCUXPRESSO \
	-D__USE_CMSIS \
	-DARM_MATH_CM7 \
	-D__NEWLIB__ \
	-DDEBUG=0 \
	-IDSP/source/ \
	-Iamazon-freertos/lib/FreeRTOS-Plus-TCP/ \
	-Iamazon-freertos/lib/FreeRTOS-Plus-TCP/portable/BufferManagement/ \
	-Iamazon-freertos/lib/FreeRTOS-Plus-TCP/portable/NetworkInterface/imxrt105x/ \
	-Iamazon-freertos/lib/FreeRTOS/ \
	-Iamazon-freertos/lib/include/ \
	-Iamazon-freertos/lib/FreeRTOS/portable/GCC/ARM_CM4F/ \
	-Iamazon-freertos/lib/FreeRTOS/portable/MemMang/ \
	-Og \
	-g3 \
	-Wall \
	-ffunction-sections \
	-fdata-sections \
	-c \
	-MMD \
	-MP \
	-Werror \
	-D"ARCPRINTF( ... )=(void)0" \
	--specs=nano.specs  \
	-Wa,-anhlmsd=build/DSP/amazon-freertos/lib/FreeRTOS-Plus-TCP/FreeRTOS_Sockets.lst \
	-o build/DSP/amazon-freertos/lib/FreeRTOS-Plus-TCP/FreeRTOS_Sockets.o amazon-freertos/lib/FreeRTOS-Plus-TCP/FreeRTOS_Sockets.c 

I have `ipconfigUSE_TCP` set to 1 in `amazon-freertos/lib/FreeRTOS-Plus-TCP/include/FreeRTOSIPConfig.h`

`FreeRTOS_Sockets.c` declares `xBoundUDPSocketsList` and `xBoundTCPSocketsList`

/* The list that contains mappings between sockets and port numbers.  Accesses
to this list must be protected by critical sections of one kind or another. */
List_t xBoundUDPSocketsList;

#if ipconfigUSE_TCP == 1
	List_t xBoundTCPSocketsList;
#endif /* ipconfigUSE_TCP == 1 */

Once I have my elf executable linked, run this command:

$ /opt/gcc-arm-none-eabi-8-2019-q3-update/bin/arm-none-eabi-nm -a -l -n -t x --print-size image/DSP.elf | grep -E '^[[:xdigit:]]{8} [[:xdigit:]]{8} B' | grep SocketsList
2001ac7c 00000014 B xBoundTCPSocketsList
2001ac90 00000014 B xBoundUDPSocketsList	/home/max/Lavori/4202/src/repos/toremove/FW/amazon-freertos/lib/FreeRTOS-Plus-TCP/FreeRTOS_Sockets.c:162

Both symbols exist in the executable, but one (`xBoundTCPSocketsList`) does not seem to belong to any .c source.
Both appear in the map file:

$ grep -n -A 1 -E 'xBoundTCPSocketsList|xBoundUDPSocketsList' image/DSP.map
61974: .bss.xBoundTCPSocketsList
61975-                0x000000002001ac7c       0x14 ./build/DSP/amazon-freertos/lib/FreeRTOS-Plus-TCP/FreeRTOS_Sockets.o
61976:                0x000000002001ac7c                xBoundTCPSocketsList
61977: .bss.xBoundUDPSocketsList
61978-                0x000000002001ac90       0x14 ./build/DSP/amazon-freertos/lib/FreeRTOS-Plus-TCP/FreeRTOS_Sockets.o
61979:                0x000000002001ac90                xBoundUDPSocketsList

Even addr2line fails:

$ arm-none-eabi-addr2line -a -e image/DSP.elf  2001ac7c 2001ac90
0x2001ac7c
??:0
0x2001ac90
/home/max/Lavori/4202/src/repos/toremove/FW/amazon-freertos/lib/FreeRTOS-Plus-TCP/FreeRTOS_Sockets.c:162

even the `FreeRTOS_Sockets.lst` doesn't tell me anything more:

 7337              		.global	xBoundTCPSocketsList
 7338              		.global	xBoundUDPSocketsList
 7339              		.section	.bss.xBoundTCPSocketsList,"aw",%nobits
 7340              		.align	2
 7341              		.set	.LANCHOR2,. + 0
 7344              	xBoundTCPSocketsList:
 7345 0000 00000000 		.space	20
 7345      00000000 
 7345      00000000 
 7345      00000000 
 7345      00000000 
 7346              		.section	.bss.xBoundUDPSocketsList,"aw",%nobits
 7347              		.align	2
 7348              		.set	.LANCHOR1,. + 0
 7351              	xBoundUDPSocketsList:
 7352 0000 00000000 		.space	20
 7352      00000000 
 7352      00000000 
 7352      00000000 
 7352      00000000 

There are many other symbols present in the executable but which do not seem to be associated with any .c source file.

Why this behavior? What changes between the two symbols `xBoundTCPSocketsList` and `xBoundUDPSocketsList`? Am I getting it wrong or omitting some debugging parameters when compiling? How do I get either nm or some other way to get the .c source where a symbol is declared?

best regards

Max

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