http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54303
Bug #: 54303
Summary: -fdata-sections -ffunction-sections and
-fmerge-constants do not work well together
Classification: Unclassified
Product: gcc
Version: 4.6.3
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
AssignedTo: unassig...@gcc.gnu.org
ReportedBy: tom.r...@gmail.com
Created attachment 28045
--> http://gcc.gnu.org/bugzilla/attachment.cgi?id=28045
Testcase for the issue
The attached test-case demonstrates the problem I see:
$ arm-linux-gnueabi-gcc -Wall -fdata-sections -ffunction-sections -o
non-collected-strings.o -c non-collected-strings.c
$ arm-linux-gnueabi-gcc -Wl,--gc-sections -o non-collected-strings
non-collected-strings.o
$ strings non-collected-strings | grep here
This string should not be here
This string should be here
$ arm-linux-gnueabi-nm non-collected-strings| grep me
00000000004004d0 t frame_dummy
00000000004004f2 T keep_me
$ arm-linux-gnueabi-nm non-collected-strings.o | grep me
0000000000000000 T garbage_collect_me
0000000000000000 T keep_me
$ arm-linux-gnueabi-objdump -h non-collected-strings.o | grep str
non-collected-strings.o: file format elf32-littlearm
3 .rodata.str1.4 0000003c 00000000 00000000 00000034 2**2
And all strings in the object file are coalesced into a single section.
Note that on x86-64 this works as expected as the last step shows instead:
$ objdump -h non-collected-strings.o | grep str
non-collected-strings.o: file format elf64-x86-64
3 .rodata.str1.8 0000001f 0000000000000000 0000000000000000 00000040 2**3
5 .rodata.str1.1 0000001b 0000000000000000 0000000000000000 0000006f 2**0
I've verified this with a few different arm-linux-gnueabi toolchains (ELDK 4.2,
ELDK 5.2.1, Linaro (4:4.6.2-7 in Ubuntu) and this seems like a long-standing
thing, not Linaro-patch specific.
