c++ - 生成文件 : error running 'make all'

Question

当我运行 make all 规则中指定的相同 gcc 命令时，我没有收到任何错误。但是当我运行 make all 时，我得到了一堆错误。为什么会这样？

生成文件:

all: program.c
      gcc -I$HOME/ffmpeg/include program.c -L$HOME/ffmpeg/lib -lswscale -lavdevice -lavfilter -lswscale -lswresample -lavformat -lavcodec -lavutil -lz -lm -lpthread -o program

运行 gcc 命令:

 (No error)

运行 make all:

gcc -IOME/ffmpeg/include program.c -LOME/ffmpeg/lib -lswscale -lavdevice -lavfilter -lswscale -lswresample -lavformat -lavcodec -lavutil -lz -lm -lpthread -o program
program.c:15:32: error: libavcodec/avcodec.h: No such file or directory
program.c:16:32: error: libswscale/swscale.h: No such file or directory
program.c:17:34: error: libavformat/avformat.h: No such file or directory
program.c:19: error: expected '=', ',', ';', 'asm' or '__attribute__' before '*' token
program.c:24: error: expected '=', ',', ';', 'asm' or '__attribute__' before '*' token
program.c:95: error: expected ')' before '*' token
program.c:128: error: expected ')' before '*' token
program.c:201: error: expected '=', ',', ';', 'asm' or '__attribute__' before '*' token
program.c: In function 'main':
program.c:253: error: 'AVFrame' undeclared (first use in this function)
program.c:253: error: (Each undeclared identifier is reported only once
program.c:253: error: for each function it appears in.)
program.c:253: error: 'loaded_image' undeclared (first use in this function)
program.c:255: error: 'img_copy' undeclared (first use in this function)
program.c:255: error: 'AV_PIX_FMT_RGB24' undeclared (first use in this function)
program.c:256: error: 'current_frame' undeclared (first use in this function)
make: *** [all] Error 1

Answer 1

$HOME 在您的 make 环境中扩展为 OME。如果你想让 shell 展开它，你需要转义它:

  gcc -I$$HOME/ffmpeg/include ...

你现在发生的事情是 make 将 $H 扩展为空，然后按原样使用该行的其余部分。