I have two very similar .so files. Using readelf --syms --wide on them I receive...
... for the first:
631: 0000000000000000 0 FUNC GLOBAL DEFAULT UND __cxa_guard_acquire@CXXABI_1.3 (18)
666: 0000000000000000 0 FUNC GLOBAL DEFAULT UND __cxa_pure_virtual@CXXABI_1.3 (18)
... for the second:
671: 0000000000000000 0 FUNC GLOBAL DEFAULT UND __cxa_guard_acquire@CXXABI_1.3 (21)
706: 0000000000000000 0 FUNC GLOBAL DEFAULT UND __cxa_pure_virtual@CXXABI_1.3 (21)
What does the (18) and (21) mean, respectively?
What does the (18) and (21) mean, respectively?
It's the value of .vd_version from corresponding version definition (ElfXX_Verdef in elf.h). For example:
readelf -Ws /bin/date | egrep ' (setenv|clock_gettime)'
14: 0000000000000000 0 FUNC GLOBAL DEFAULT UND clock_gettime@GLIBC_2.17 (5)
15: 0000000000000000 0 FUNC GLOBAL DEFAULT UND setenv@GLIBC_2.2.5 (3)
readelf -V /bin/date
...
Version needs section '.gnu.version_r' contains 1 entry:
Addr: 0x0000000000000fd8 Offset: 0x000fd8 Link: 6 (.dynstr)
000000: Version: 1 File: libc.so.6 Cnt: 6
0x0010: Name: GLIBC_2.14 Flags: none Version: 7
0x0020: Name: GLIBC_2.4 Flags: none Version: 6
0x0030: Name: GLIBC_2.17 Flags: none Version: 5
0x0040: Name: GLIBC_2.3.4 Flags: none Version: 4
0x0050: Name: GLIBC_2.2.5 Flags: none Version: 3
0x0060: Name: GLIBC_2.3 Flags: none Version: 2
Note that GLIBC_2.2.5 has Version: 3 and GLIBC_2.17 has Version: 5.