makefile中的变量扩展

Make似乎仅在激活规则后才扩展变量

make ok

显示已解析的名称（即“test”）

makebad

声称依赖于“grep”（而不是“test”）

在检查“坏”规则的依赖项之前，如何让

make

展开NAME

CMakeLists.txt：

add_executable(test testA.c testB.c)  # compiler (output input input ...)

生成文件（完整）：

#========================================
# Shell cannot handle parentheses:
#    *** unterminated call to function 'shell': missing ')'.  Stop.
# Have also tried putting {"(", ")", "\(", "\)"} in variables
#   ...but it just created a different problem
#
#NAME := $(shell grep "add_executable(" CMakeLists.txt | sed 's/[^(]*( *\([^ ]*\) .*/\1/')
  
#========================================
# Curious results (same with or without the colon)
#
NAME := `grep "add_executable(" CMakeLists.txt | sed 's/[^(]*( *\([^ ]*\) .*/\1/'`
    
#========================================
# As expected, displays:
#    NAME=¦test¦"
#
PHONY: ok
ok:
    @echo "NAME=¦${NAME}¦"
 
#========================================
# Dies with:
#    *** No rule to make target '`grep', needed by 'bad'.  Stop."
#
.PHONY: bad
bad: ${NAME}
    @echo "NAME=¦${NAME}¦"

NAME := `grep "add_executable(" CMakeLists.txt | sed 's/[^(]*( *\([^ ]*\) .*/\1/'`
ok:
    @echo "NAME=¦${NAME}¦"
bad: ${NAME}
    @echo "NAME=¦${NAME}¦"

生成文件（相同，但压缩）：

#========================================
# Shell cannot handle parentheses:
#    *** unterminated call to function 'shell': missing ')'.  Stop.
# Have also tried putting {"(", ")", "\(", "\)"} in variables
#   ...but it just created a different problem
#
#NAME := $(shell grep "add_executable(" CMakeLists.txt | sed 's/[^(]*( *\([^ ]*\) .*/\1/')
  
#========================================
# Curious results (same with or without the colon)
#
NAME := `grep "add_executable(" CMakeLists.txt | sed 's/[^(]*( *\([^ ]*\) .*/\1/'`
    
#========================================
# As expected, displays:
#    NAME=¦test¦"
#
PHONY: ok
ok:
    @echo "NAME=¦${NAME}¦"
 
#========================================
# Dies with:
#    *** No rule to make target '`grep', needed by 'bad'.  Stop."
#
.PHONY: bad
bad: ${NAME}
    @echo "NAME=¦${NAME}¦"

NAME := `grep "add_executable(" CMakeLists.txt | sed 's/[^(]*( *\([^ ]*\) .*/\1/'`
ok:
    @echo "NAME=¦${NAME}¦"
bad: ${NAME}
    @echo "NAME=¦${NAME}¦"

---

使用以下命令代替反引号：

---

（在

shell

命令中使用大括号而不是圆括号是一个很难在

sed

命令中使用圆括号的地方，我不知道如何优雅地转义。）

这里有一个粗略的解决方案，在我（或其他人）想出一个更优雅的解决方案之前，它将一直有效：

NAME:=$（shell sed-n）/add\u/{s/add|u executable.*/；s/*/；p；}“CMakeLists.txt）

非常感谢您向我展示了如何清理

grep | sed

：）谢谢。