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Dan Albert 2014-10-11 00:48:32 +00:00 committed by Gerrit Code Review
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README.md
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@ -4,40 +4,52 @@ Working on bionic
What are the big pieces of bionic?
----------------------------------
libc/ --- libc.so, libc.a
The C library. Stuff like fopen(3) and kill(2).
libm/ --- libm.so, libm.a
The math library. Traditionally Unix systems kept stuff like sin(3) and
cos(3) in a separate library to save space in the days before shared
libraries.
libdl/ --- libdl.so
The dynamic linker interface library. This is actually just a bunch of
stubs that the dynamic linker replaces with pointers to its own
implementation at runtime. This is where stuff like dlopen(3) lives.
libstdc++/ --- libstdc++.so
The C++ ABI support functions. The C++ compiler doesn't know how to
implement thread-safe static initialization and the like, so it just calls
functions that are supplied by the system. Stuff like __cxa_guard_acquire
and __cxa_pure_virtual live here.
#### libc/ --- libc.so, libc.a
linker/ --- /system/bin/linker and /system/bin/linker64
The dynamic linker. When you run a dynamically-linked executable, its ELF
file has a DT_INTERP entry that says "use the following program to start me".
On Android, that's either linker or linker64 (depending on whether it's a
32-bit or 64-bit executable). It's responsible for loading the ELF executable
into memory and resolving references to symbols (so that when your code tries
to jump to fopen(3), say, it lands in the right place).
The C library. Stuff like `fopen(3)` and `kill(2)`.
tests/ --- unit tests
The tests/ directory contains unit tests. Roughly arranged as one file per
publicly-exported header file.
benchmarks/ --- benchmarks
The benchmarks/ directory contains benchmarks.
#### libm/ --- libm.so, libm.a
The math library. Traditionally Unix systems kept stuff like `sin(3)` and
`cos(3)` in a separate library to save space in the days before shared
libraries.
#### libdl/ --- libdl.so
The dynamic linker interface library. This is actually just a bunch of stubs
that the dynamic linker replaces with pointers to its own implementation at
runtime. This is where stuff like `dlopen(3)` lives.
#### libstdc++/ --- libstdc++.so
The C++ ABI support functions. The C++ compiler doesn't know how to implement
thread-safe static initialization and the like, so it just calls functions that
are supplied by the system. Stuff like `__cxa_guard_acquire` and
`__cxa_pure_virtual` live here.
#### linker/ --- /system/bin/linker and /system/bin/linker64
The dynamic linker. When you run a dynamically-linked executable, its ELF file
has a `DT_INTERP` entry that says "use the following program to start me". On
Android, that's either `linker` or `linker64` (depending on whether it's a
32-bit or 64-bit executable). It's responsible for loading the ELF executable
into memory and resolving references to symbols (so that when your code tries to
jump to `fopen(3)`, say, it lands in the right place).
#### tests/ --- unit tests
The `tests/` directory contains unit tests. Roughly arranged as one file per
publicly-exported header file.
#### benchmarks/ --- benchmarks
The `benchmarks/` directory contains benchmarks.
What's in libc/?
----------------
<pre>
libc/
arch-arm/
arch-arm64/
@ -121,6 +133,7 @@ libc/
zoneinfo/
# Android-format time zone data.
# See 'Updating tzdata' later.
</pre>
Adding system calls