libvpx:编译简单的编码器示例

Question

我正在尝试编译Googles libvpx编码器示例，可以在这里找到：

http://www.webmproject.org/docs/vp8-sdk/example__simple__encoder.html

不幸的是，libvpx似乎遗漏了依赖关系：

/usr/local/lib/libvpx.a(rdopt.c.o): In function `vp8_initialize_rd_consts':
(.text+0x3519): undefined reference to `pow'
/usr/local/lib/libvpx.a(onyx_if.c.o): In function `vp8_create_compressor':
(.text+0x34a8): undefined reference to `log'
/usr/local/lib/libvpx.a(psnr.c.o): In function `vp8_mse2psnr':
(.text+0x1f): undefined reference to `log10'
/usr/local/lib/libvpx.a(postproc.c.o):(.text+0xa4): undefined reference to `exp'
/usr/local/lib/libvpx.a(postproc.c.o): In function `vp8_gaussian':
(.text+0x11d2): undefined reference to `exp'
/usr/local/lib/libvpx.a(firstpass.c.o):(.text+0x539): undefined reference to `pow'
/usr/local/lib/libvpx.a(firstpass.c.o):(.text+0x5b6): undefined reference to `pow'
/usr/local/lib/libvpx.a(firstpass.c.o):(.text+0x8cb): undefined reference to `pow'
/usr/local/lib/libvpx.a(firstpass.c.o):(.text+0xb52): undefined reference to `sqrt'
/usr/local/lib/libvpx.a(firstpass.c.o):(.text+0xca3): undefined reference to `pow'
/usr/local/lib/libvpx.a(firstpass.c.o): In function `vp8_init_second_pass':
(.text+0x22b2): undefined reference to `pow'
/usr/local/lib/libvpx.a(firstpass.c.o): In function `vp8_init_second_pass':
(.text+0x2376): undefined reference to `pow'
/usr/local/lib/libvpx.a(firstpass.c.o): In function `vp8_second_pass':
(.text+0x26c6): undefined reference to `log'
/usr/local/lib/libvpx.a(firstpass.c.o): In function `vp8_second_pass':
(.text+0x26df): undefined reference to `log'
/usr/local/lib/libvpx.a(firstpass.c.o): In function `vp8_second_pass':
(.text+0x26f6): undefined reference to `log'
/usr/local/lib/libvpx.a(firstpass.c.o): In function `vp8_second_pass':
(.text+0x2f39): undefined reference to `pow'
/usr/local/lib/libvpx.a(firstpass.c.o): In function `vp8_second_pass':
(.text+0x300e): undefined reference to `pow'
/usr/local/lib/libvpx.a(firstpass.c.o): In function `vp8_second_pass':
(.text+0x3790): undefined reference to `pow'
/usr/local/lib/libvpx.a(firstpass.c.o): In function `vp8_second_pass':
(.text+0x387d): undefined reference to `pow'
/usr/local/lib/libvpx.a(firstpass.c.o): In function `vp8_second_pass':
(.text+0x3c6d): undefined reference to `pow'
/usr/local/lib/libvpx.a(firstpass.c.o):(.text+0x486f): more undefined references to `pow' follow
/usr/local/lib/libvpx.a(firstpass.c.o): In function `vp8_second_pass':
(.text+0x7208): undefined reference to `sqrt'
/usr/local/lib/libvpx.a(firstpass.c.o): In function `vp8_second_pass':
(.text+0x7264): undefined reference to `sqrt'
/usr/local/lib/libvpx.a(firstpass.c.o): In function `vp8_second_pass':
(.text+0x72b8): undefined reference to `sqrt'
/usr/local/lib/libvpx.a(firstpass.c.o): In function `vp8_second_pass':
(.text+0x7330): undefined reference to `sqrt'
/usr/local/lib/libvpx.a(firstpass.c.o): In function `vp8_second_pass':
(.text+0x73c1): undefined reference to `sqrt'

我使用的是Fedora18 x64，并且已经从源代码构建了libvpx (make + make install)，所以一切都应该就绪。还有谁遇到过这个问题？

Answer 1

你没有链接数学库，-lm

Answer 2

你在静态链接libvpx吗？你可以只使用-lvpx来动态链接。我没有遇到这个问题(ubuntu12.10，x64，vpx源码构建，gcc 4.7.2)。

无论如何，pow、exp、sqrt等都是libm的一部分，libm是编译器附带的数学库，所以只需将-lm添加到链接器标志中，这些错误就会消失。