Here is the objdump -dr bin/autoboot.o output we want (using the glibc
weak alias technique):
20e: e8 fc ff ff ff call 20f <netboot+0xe2>
20f: R_386_PC32 printf
213: 89 f0 mov %esi,%eax
215: e8 fc ff ff ff call 216 <netboot+0xe9>
216: R_386_PC32 pxe_menu_boot
Notice that pxe_menu_boot is a relocation because at this point the
toolchain doesn't know whether or not to use the weak symbol yet.
Here is the broken objdump -dr bin/autoboot.o output we currently have
in gpxe.git:
00000000 <pxe_menu_boot>:
0: b8 fd 1f fc c3 mov $0xc3fc1ffd,%eax
5: c3 ret
[...]
20d: e8 fc ff ff ff call 20e <netboot+0xe1>
20e: R_386_PC32 printf
212: bf fd 1f fc c3 mov $0xc3fc1ffd,%edi
The compiler has inlined pxe_menu_boot, there is no relocation!
Here is what readelf -a bin/autoboot.o says about the broken autoboot.o:
Num: Value Size Type Bind Vis Ndx Name
23: 00000000 6 FUNC WEAK HIDDEN 1 pxe_menu_boot
I don't see anything particularly interesting in this readelf output
but I put it here for completeness.
So it seems that gcc inlined the function when it shouldn't have.
Here is what happens when CFLAGS += -Os is changed to CFLAGS += -O in
Makefile.housekeeping:
2ad: e8 fc ff ff ff call 2ae <netboot+0xf0>
2ae: R_386_PC32 printf
2b2: 89 f0 mov %esi,%eax
2b4: e8 fc ff ff ff call 2b5 <netboot+0xf7>
2b5: R_386_PC32 pxe_menu_boot
Suddenly there is a relocation for pxe_menu_boot again!
Compiler bug or do we not understand __attribute__ ((weak)) properly?
The plot thickens...
Stefan
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