GNU make manual 翻译( 九十六)
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4.5.6 Directory Search for Link Libraries ----------------------------------------- Directory search applies in a special way to libraries used with the linker. This special feature comes into play when you write a prerequisite whose name is of the form `-lNAME'. (You can tell something strange is going on here because the prerequisite is normally the name of a file, and the _file name_ of a library generally looks like `libNAME.a', not like `-lNAME'.) When a prerequisite's name has the form `-lNAME', `make' handles it specially by searching for the file `libNAME.so', and, if it is not found, for the file `libNAME.a' in the current directory, in directories specified by matching `vpath' search paths and the `VPATH' search path, and then in the directories `/lib', `/usr/lib', and `PREFIX/lib' (normally `/usr/local/lib', but MS-DOS/MS-Windows versions of `make' behave as if PREFIX is defined to be the root of the DJGPP installation tree). For example, if there is a `/usr/lib/libcurses.a' library on your system (and no `/usr/lib/libcurses.so' file), then foo : foo.c -lcurses cc $^ -o $@ would cause the command `cc foo.c /usr/lib/libcurses.a -o foo' to be executed when `foo' is older than `foo.c' or than `/usr/lib/libcurses.a'.
4.5.6 对链接库的目录搜索
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对被链接器所使用的库，目录搜索采用特殊的方式。当你以-lNMAE格式来写前提条件时，这种特殊的功能将其作用。(你可以说有些奇怪的事情正在进行，因为正常的前提条件是一个文件的民自，并且一个库的文件名通常是 libNMAE.a 之类，而不是 像 -lNMAE 的样子)
当一个前提条件的名字中有 -lNAME 的格式，make 要对其进行特殊处理，搜索 libNAME.so ，如果没有找到，则搜索 libNAME.a。此种搜索是在 当前目录和vpath 搜索路径和 VPATH 搜索路径中进行，再然后是 /lib， /usr/lib ，PREFIX/lib (通常是 /usr/local/lib ，但是 MS-DOS/MS-Windows 版本的make 会把PREFIX 处理成 DJGPP 安装目录的根目录)
例如，如果有你的系统里有一个 /usr/lib/libcurses.a 库(并且没有 /usr/lib/libcurses.so 文件)则
foo : foo.c -lcurses
cc $^ -o $@
将会导致，如果foo比 foo.c 或者 /usr/lib/libcurses.a 旧，则执行 cc foo.c /usr/lib/libcurses.a -o foo
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