42

ld 的这个选项是什么意思？

-lrt

我知道在某种程度上这意味着 ld 正在寻找具有实时扩展功能的库，但是经过广泛搜索后，我找不到确切的定义（或哪个库）。

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

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

编辑

从仿生概述

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

- 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 库中。

问题是 collect2 将选项 -lrt（以及 -lpthreads）传递给 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？

4

3 回答 3

46

当您看到 时-lsomething，库名称是libsomething。做一个man librt说以下：

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.
于 2011-07-19T21:00:46.537 回答
7

-l是用于将库链接到最终可执行文件的标志。在这种情况下，有问题的库是librt.a（或librt.so或librt.dylib，取决于您的系统）。 librt是实时扩展库。

于 2011-07-19T20:57:11.273 回答
5

回答我自己的问题：它被硬编码到 gdc/d/d-spec.c

于 2011-07-20T02:36:46.463 回答