ld 选项 -lrt 指的是什么库(Bionic libc)? [英] What library does ld option -lrt refer to (Bionic libc)?

问题描述

ld 的这个选项是什么意思?

What does this option to ld mean?

-lrt

我在某种程度上知道这意味着 ld 正在寻找具有实时扩展功能的库，但经过广泛搜索后，我找不到确切的定义(或所指的库).

I know to some degree it means that ld is looking for the library with real-time extensions, but after searching extensively, I couldn't find an exact definition (or which library) this is referring to.

对于 Bionic (android) libc，android NDK 文档详细说明了它(连同 pthreads)已被集成.

With Bionic (android) libc, the android NDK docs detail that this (along with pthreads) has been integrated.

我问是因为它似乎是隐式的(即当我直接调用编译器，一个自定义编译的 gdc 时，我收到一条消息说 ld 找不到 -lrt)

I ask because it seems to be implicit (ie when I invoke the compiler, a custom-compiled gdc, directly, I get a message saying that ld cannot find -lrt)

编辑

来自仿生概述

Bionic 的 C 库附带捆绑了自己的 pthread 实现in. 这与其他历史上的 C 库不同:

Bionic's C library comes with its own pthread implementation bundled in. This is different from other historical C libraries which:

- place it in an external library (-lpthread)
- play linker tricks with weak symbols at dynamic link time

对实时功能(又名-lrt)的支持也捆绑在C 库.

The support for real-time features (a.k.a. -lrt) is also bundled in the C library.

问题在于 collect2 将选项 -lrt(以及 -lpthreads)传递给 ld.

The problem is that collect2 is passing the option -lrt (and also -lpthreads) to ld.

dan@devbox:~/projects/gdc_test/jni/src$ $DC gdc_test.d -v -mthumb
Using built-in specs.
Target: arm-linux-androideabi
Configured with: /arm/ndk-git/src/build/../gcc/gcc-4.4.3/configure --prefix=/arm/ndk-git/ndk/toolchains/arm-linux-androideabi-4.4.3/prebuilt/linux-x86 --target=arm-linux-androideabi --host=x86_64-linux-gnu --build=x86_64-linux-gnu --with-gnu-as --with-gnu-ld --enable-languages=c,c++ --with-gmp=/arm/ndk-git/build_run/temp-install --with-mpfr=/arm/ndk-git/build_run/temp-install --disable-libssp --enable-threads --disable-nls --disable-libmudflap --disable-libgomp --disable-libstdc__-v3 --disable-sjlj-exceptions --disable-shared --disable-tls --enable-languages=c,d,c++ --enable-lto --with-float=soft --with-fpu=vfp --with-arch=armv5te --enable-target-optspace --enable-shared--prefix=/arm/ndk-git/ndk/toolchains/arm-linux-androideabi-4.4.3/prebuilt/linux-x86 --enable-initfini-array --disable-nls --prefix=/arm/ndk-git/ndk/toolchains/arm-linux-androideabi-4.4.3/prebuilt/linux-x86 --with-sysroot=/arm/ndk-git/ndk/toolchains/arm-linux-androideabi-4.4.3/prebuilt/linux-x86/sysroot --with-binutils-version=2.19 --with-mpfr-version=2.4.1 --with-gmp-version=4.2.4 --with-gcc-version=4.4.3 --with-gdb-version=6.6 --with-arch=armv5te --enable-libstdc__-v3 --disable-werrors --enable-languages=c,d,c++ --enable-shared --enable-multilib --disable-threads --program-transform-name='s,^,arm-linux-androideabi-,'
Thread model: single
gcc version 4.4.3 20100121 (gdc hg, using dmd 1.067) (GCC) 
COLLECT_GCC_OPTIONS='-v' '-mthumb' '-shared-libgcc' '-pthread' '-march=armv5te' '-mfloat-abi=soft' '-mfpu=vfp'
 /home/dan/projects/arm-linux-androideabi-4.4.3/bin/../libexec/gcc/arm-linux-androideabi/4.4.3/cc1d gdc_test.d -mbionic -fpic -quiet -dumpbase gdc_test.d -mthumb -march=armv5te -mfloat-abi=soft -mfpu=vfp -auxbase gdc_test -version -imultilib thumb -iprefix /home/dan/projects/arm-linux-androideabi-4.4.3/bin/../lib/gcc/arm-linux-androideabi/4.4.3/ -isysroot /home/dan/projects/arm-linux-androideabi-4.4.3/bin/../sysroot -fmultilib-dir=thumb -o /tmp/cc2yu97y.s
GNU D (GCC) version 4.4.3 20100121 (gdc hg, using dmd 1.067) (arm-linux-androideabi)
    compiled by GNU C version 4.5.2, GMP version 4.2.4, MPFR version 2.4.1.
GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
GNU D (GCC) version 4.4.3 20100121 (gdc hg, using dmd 1.067) (arm-linux-androideabi)
    compiled by GNU C version 4.5.2, GMP version 4.2.4, MPFR version 2.4.1.
GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
COLLECT_GCC_OPTIONS='-v' '-mthumb' '-shared-libgcc' '-pthread' '-march=armv5te' '-mfloat-abi=soft' '-mfpu=vfp'
 /home/dan/projects/arm-linux-androideabi-4.4.3/bin/../lib/gcc/arm-linux-androideabi/4.4.3/../../../../arm-linux-androideabi/bin/as -v -march=armv5te -mfloat-abi=soft -mfpu=vfp -meabi=5 -o /tmp/ccuFGEfj.o /tmp/cc2yu97y.s
GNU assembler version 2.19 (arm-linux-androideabi) using BFD version (GNU Binutils) 2.19
COMPILER_PATH=/home/dan/projects/arm-linux-androideabi-4.4.3/bin/../libexec/gcc/arm-linux-androideabi/4.4.3/:/home/dan/projects/arm-linux-androideabi-4.4.3/bin/../libexec/gcc/:/home/dan/projects/arm-linux-androideabi-4.4.3/bin/../lib/gcc/arm-linux-androideabi/4.4.3/../../../../arm-linux-androideabi/bin/
LIBRARY_PATH=/home/dan/projects/arm-linux-androideabi-4.4.3/bin/../lib/gcc/arm-linux-androideabi/4.4.3/thumb/:/home/dan/projects/arm-linux-androideabi-4.4.3/bin/../lib/gcc/arm-linux-androideabi/4.4.3/../../../../arm-linux-androideabi/lib/thumb/:/home/dan/projects/arm-linux-androideabi-4.4.3/bin/../lib/gcc/arm-linux-androideabi/4.4.3/:/home/dan/projects/arm-linux-androideabi-4.4.3/bin/../lib/gcc/:/home/dan/projects/arm-linux-androideabi-4.4.3/bin/../lib/gcc/arm-linux-androideabi/4.4.3/../../../../arm-linux-androideabi/lib/:/home/dan/projects/arm-linux-androideabi-4.4.3/bin/../sysroot/usr/lib/
COLLECT_GCC_OPTIONS='-v' '-mthumb' '-shared-libgcc' '-pthread' '-march=armv5te' '-mfloat-abi=soft' '-mfpu=vfp'
 /home/dan/projects/arm-linux-androideabi-4.4.3/bin/../libexec/gcc/arm-linux-androideabi/4.4.3/collect2 --sysroot=/home/dan/projects/arm-linux-androideabi-4.4.3/bin/../sysroot --eh-frame-hdr -dynamic-linker /system/bin/linker -X -m armelf_linux_eabi /home/dan/projects/arm-linux-androideabi-4.4.3/bin/../sysroot/usr/lib/crtbegin_dynamic.o -L/home/dan/projects/arm-linux-androideabi-4.4.3/bin/../lib/gcc/arm-linux-androideabi/4.4.3/thumb -L/home/dan/projects/arm-linux-androideabi-4.4.3/bin/../lib/gcc/arm-linux-androideabi/4.4.3/../../../../arm-linux-androideabi/lib/thumb -L/home/dan/projects/arm-linux-androideabi-4.4.3/bin/../lib/gcc/arm-linux-androideabi/4.4.3 -L/home/dan/projects/arm-linux-androideabi-4.4.3/bin/../lib/gcc -L/home/dan/projects/arm-linux-androideabi-4.4.3/bin/../lib/gcc/arm-linux-androideabi/4.4.3/../../../../arm-linux-androideabi/lib -L/home/dan/projects/arm-linux-androideabi-4.4.3/bin/../sysroot/usr/lib /tmp/ccuFGEfj.o -lgphobos -lm -lrt -lgcc_s -lgcc -lpthread -lc -ldl -lgcc_s -lgcc /home/dan/projects/arm-linux-androideabi-4.4.3/bin/../sysroot/usr/lib/crtend_android.o
/home/dan/projects/arm-linux-androideabi-4.4.3/bin/../lib/gcc/arm-linux-androideabi/4.4.3/../../../../arm-linux-androideabi/bin/ld: cannot find -lrt
collect2: ld returned 1 exit status

有没有办法覆盖这种行为?

Is there a way to override this behavior?

推荐答案

当你看到 -lsomething 时，库名称是 libsomething.执行 man librt 说明如下:

When you see a -lsomething, the library name is libsomething. Doing a man librt says the following:

NAME
     librt, libposix4 - POSIX.1b Realtime Extensions library

SYNOPSIS
     cc [ flag... ] file... -lrt [ library... ]

DESCRIPTION
     Functions in this library provide  most  of  the  interfaces
     specified  by  the  POSIX.1b  Realtime Extension.  See stan-
     dards(5). Specifically, this includes the interfaces defined
     under   the   Asynchronous  I/O,  Message  Passing,  Process
     Scheduling, Realtime Signals Extension,  Semaphores,  Shared
     Memory  Objects,  Synchronized  I/O, and Timers options. The
     interfaces defined under the Memory  Mapped  Files,  Process
     Memory  Locking,  and  Range Memory Locking options are pro-
     vided in libc(3LIB)

     See the man pages for the individual interfaces  in  section
     3RT for information on required headers.

     The name libposix4 is maintained for backward  compatibility
     and  should be avoided. librt is the preferred name for this
     library.

这篇关于ld 选项 -lrt 指的是什么库(Bionic libc)?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！