I am using zig from zig-linux-x86_64-0.12.0-dev.1856+94c63f31f.tar.xz.
I create asd.zig file: |
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I build libasd.so shared library: |
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I check libasd.so file size: |
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I edit asd.zig file: |
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I build libasd.so shared library again: |
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I check libasd.so file size: |
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I get surprised that libasd.so became approximately 112 times bigger: |
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Because lemcmp does not exist (unlike memcmp) and therefore was not included in the .so , thus making the .so smaller?
libasd.so (small) as lemcmp/libasd.so and new (big) libasd.so as memcmp/libasd.so.lemcmp/libasd.so or memcmp/libasd.so depend on libc.so.6 (there is no (NEEDED)):$ readelf -d lemcmp/libasd.soDynamic section at offset 0x320 contains 13 entries:
Tag Type Name/Value
0x000000000000000e (SONAME) Library soname: [libasd.so]
0x000000000000001e (FLAGS) BIND_NOW
0x000000006ffffffb (FLAGS_1) Flags: NOW
0x0000000000000007 (RELA) 0x2a0
0x0000000000000008 (RELASZ) 24 (bytes)
0x0000000000000009 (RELAENT) 24 (bytes)
0x0000000000000006 (SYMTAB) 0x200
0x000000000000000b (SYMENT) 24 (bytes)
0x0000000000000005 (STRTAB) 0x288
0x000000000000000a (STRSZ) 22 (bytes)
0x000000006ffffef5 (GNU_HASH) 0x248
0x0000000000000004 (HASH) 0x268
0x0000000000000000 (NULL) 0x0
$ readelf -d memcmp/libasd.soDynamic section at offset 0x25c50 contains 17 entries:
Tag Type Name/Value
0x000000000000000e (SONAME) Library soname: [libasd.so]
0x000000000000001e (FLAGS) BIND_NOW
0x000000006ffffffb (FLAGS_1) Flags: NOW
0x0000000000000007 (RELA) 0x5760
0x0000000000000008 (RELASZ) 24 (bytes)
0x0000000000000009 (RELAENT) 24 (bytes)
0x0000000000000017 (JMPREL) 0x5778
0x0000000000000002 (PLTRELSZ) 1488 (bytes)
0x0000000000000003 (PLTGOT) 0x27d68
0x0000000000000014 (PLTREL) RELA
0x0000000000000006 (SYMTAB) 0x238
0x000000000000000b (SYMENT) 24 (bytes)
0x0000000000000005 (STRTAB) 0x44b8
0x000000000000000a (STRSZ) 4773 (bytes)
0x000000006ffffef5 (GNU_HASH) 0x2ab8
0x0000000000000004 (HASH) 0x3730
0x0000000000000000 (NULL) 0x0
memcmp exists.$ readelf -d /usr/lib/libbz2.so.1.0 (that does depend on libc.so.6)Dynamic section at offset 0x11e40 contains 28 entries:
Tag Type Name/Value
0x00000001 (NEEDED) Shared library: [libc.so.6]
0x0000000e (SONAME) Library soname: [libbz2.so.1]
0x0000000c (INIT) 0x1000
0x0000000d (FINI) 0xee54
0x00000019 (INIT_ARRAY) 0x12df8
0x0000001b (INIT_ARRAYSZ) 4 (bytes)
0x0000001a (FINI_ARRAY) 0x12dfc
0x0000001c (FINI_ARRAYSZ) 4 (bytes)
0x00000004 (HASH) 0x1c0
0x6ffffef5 (GNU_HASH) 0x324
0x00000005 (STRTAB) 0x718
0x00000006 (SYMTAB) 0x3f8
0x0000000a (STRSZ) 723 (bytes)
0x0000000b (SYMENT) 16 (bytes)
0x00000003 (PLTGOT) 0x12f40
0x00000002 (PLTRELSZ) 256 (bytes)
0x00000014 (PLTREL) REL
0x00000017 (JMPREL) 0xb90
0x00000011 (REL) 0xac0
0x00000012 (RELSZ) 208 (bytes)
0x00000013 (RELENT) 8 (bytes)
0x0000001e (FLAGS) BIND_NOW
0x6ffffffb (FLAGS_1) Flags: NOW
0x6ffffffe (VERNEED) 0xa50
0x6fffffff (VERNEEDNUM) 1
0x6ffffff0 (VERSYM) 0x9ec
0x6ffffffa (RELCOUNT) 19
0x00000000 (NULL) 0x0
asd.zig is:
extern var strcmp: isize;
export fn asd() callconv(.C) isize {
return strcmp;
}
$ zig build-lib -dynamic -O ReleaseFast asd.zig
$ du --bytes libasd.so
7624 libasd.so
libasd.so is not big (same file size as lemcmp/libasd.so)
nm -D memcmp/libasd.so):extern one of them, you get them all (in nm -D libasd.so)!
zig-linux-x86_64-0.14.0-dev.2050+4adf63aef.tar.xz still has this problem and there are more special symbol names:no answers here, so I made github issue: some symbol names cause bloat · Issue #21848 · ziglang/zig · GitHub
Vexu's comment on github issue:
__bitreversedi2is a compiler-rt symbol so using it causes compiler-rt to be statically linked into the library. You can prevent that with-fno-compiler-rtbut doing so might cause other problems.