Unexpected growth of files between v19 and v24

For Developers
1

I used to work with OpenWRT 19 and I am building the OpenWRT 24.
I noticed that some stripped libraries and binaries files are 65k in size, but they should be smaller.

For example, package json-c:

  • Opewrt 19 (gcc 7.5.0)
    build_dir/target-mips_24kc_musl/json-c-0.12.1/ipkg-mips_24kc/libjson-c/usr/lib/libjson-c.so.2.0.2 = 29K

  • Openwrt 24 (gcc 13.3.0)
    build_dir/target-mips_24kc_musl/json-c-0.18/ipkg-mips_24kc/libjson-c/usr/lib/libjson-c.so.5.4.0 = 65K

I know the json-c version is different, but for sure it is not the reason of this difference.

Looking into the binary from Openwrt 24, it seems related to the eh_frame section:

  [17] .eh_frame         PROGBITS        0000ac4c 00ac4c 000004 00   A  0   0  4
  [18] .tbss             NOBITS          0001fe78 00fe78 000004 00 WAT  0   0  4

The offset was expected to be AC50, but it is 00fe78. that's about 21k larger.

I have also passed some arguments on CFLAGS to remove eh_frame, but the stripped file is alway 65k.

2

The reason is the "relro" option:

+CONFIG_PKG_RELRO_NONE=y
+# CONFIG_PKG_RELRO_PARTIAL is not set
+# CONFIG_PKG_RELRO_FULL is not set

I'm not sure why, but it's adding more overhead to the file than expected.