[Bug] DWARF-5 section names in PE/PEP and weak symbols

Achim Gratz Stromeko@nexgo.de
Tue Feb 15 19:08:10 GMT 2022


Achim Gratz writes:
> So, snprintf seems to behave as expected (it resolves NULL) and the two
> other symbols are resolved even though they should not.  If they had
> resolved to the actual address things might even work, but the actual
> values explain nicely why a program calling through the pointer crashes
> in various horrible ways (depending on what actually is mapped there).

So I've removed the "weak" attribute from snprintf so that it links:

--8<---------------cut here---------------start------------->8---
...packages/binutils-gdb/build (2139)# 
...packages/binutils-gdb/build (2139)# objdump -x /usr/lib/libcygwin.a |less
...packages/binutils-gdb/build (2140)# gcc -Wl,--trace-symbol={fputs,snprintf,thrd_exit} -c -o weak_test.o weak_test.c
...packages/binutils-gdb/build (2141)# gcc -Wl,--trace-symbol={fputs,{a,v,}snprintf,thrd_exit} -o weak_test weak_test.o
/usr/lib/gcc/x86_64-pc-cygwin/11/../../../../x86_64-pc-cygwin/bin/ld: weak_test.o: reference to snprintf
/usr/lib/gcc/x86_64-pc-cygwin/11/../../../../x86_64-pc-cygwin/bin/ld: weak_test.o: reference to thrd_exit
/usr/lib/gcc/x86_64-pc-cygwin/11/../../../../x86_64-pc-cygwin/bin/ld: weak_test.o: reference to fputs
/usr/lib/gcc/x86_64-pc-cygwin/11/../../../../x86_64-pc-cygwin/bin/ld: /usr/lib/gcc/x86_64-pc-cygwin/11/../../../../lib/libcygwin.a(t-d000578.o): definition of fputs
/usr/lib/gcc/x86_64-pc-cygwin/11/../../../../x86_64-pc-cygwin/bin/ld: /usr/lib/gcc/x86_64-pc-cygwin/11/../../../../lib/libcygwin.a(t-d001396.o): definition of snprintf
/usr/lib/gcc/x86_64-pc-cygwin/11/../../../../x86_64-pc-cygwin/bin/ld: /usr/lib/gcc/x86_64-pc-cygwin/11/../../../../lib/libcygwin.a(t-d001527.o): definition of thrd_exit
...packages/binutils-gdb/build (2142)# ./weak_test ; echo $?
snprintf  => 0x0001004012e0     is not equal NULL
fputs     => 0x0001004012c0     is not equal NULL
thrd_exit => 0x0001004012f0     is not equal NULL
sprintf called through symbol
0
...packages/binutils-gdb/build (2143)# nm weak_test.o /bin/cygwin1.dll | egrep ' (fputs|[av]?snprintf|thrd_exit)$'
                 U fputs
                 U snprintf
                 U thrd_exit
00000001801abb10 T asnprintf
00000001801b1610 T fputs
00000001801c0380 T snprintf
00000001801849a0 T thrd_exit
00000001801eec30 T vsnprintf
--8<---------------cut here---------------end--------------->8---


Regards,
Achim.
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