RetroBSD Makefile转CMake：Shell输出重定向编译问题解决

将RetroBSD项目的Makefile迁移至CMake时，卡在了模拟原Makefile中Shell脚本输出重定向到编译器的逻辑上。原Makefile通过printf生成代码，再通过管道传给编译器编译成目标文件。尝试用add_custom_target实现时，无论是否设置VERBATIM，生成的Makefile都会出现引号或转义字符问题，导致编译器无法识别CFLAGS参数，最终通过移除CMAKE_C_FLAGS定义中的引号和COMMAND中的引号解决了问题。

原始Makefile片段 #

all:            ../libc.a

../libc.a:      ../ar ../ranlib $(OBJS)
                ../ar rc $@ $(OBJS)
                ../ranlib $@

$(OBJS):     $(LIBCDIR)/mips/sys/SYS.h
                @echo creating $*.o
                @printf '#include "SYS.h"
SYS($*)
' | $(CMAKE_C_COMPILER) $(CMAKE_C_FLAGS) - -c -o $*.o

尝试的CMakeLists.txt片段 #

cmake_minimum_required(VERSION 3.20)
project(myRetroBSD_native_libc LANGUAGES C)

set(OBJ_FILES
__sysctl
accept
)

set(OBJECT_OUTPUT_DIR ${CMAKE_BINARY_DIR}/objs)

file(MAKE_DIRECTORY ${OBJECT_OUTPUT_DIR})

foreach(OBJ_FILE ${OBJ_FILES})

    file(GENERATE OUTPUT ${OBJECT_OUTPUT_DIR}/${OBJ_FILE}.sh CONTENT "printf '#include \"SYS.h\"\nSYS(${OBJ_FILE})\n'")
    
    add_custom_target(
        ${OBJ_FILE} ALL
        COMMAND bash "${OBJECT_OUTPUT_DIR}/${OBJ_FILE}.sh | ${CMAKE_C_COMPILER} ${CMAKE_C_FLAGS} - -c -o ${OBJECT_OUTPUT_DIR}/${OBJ_FILE}.o "
        VERBATIM
    )

endforeach()

错误信息 #

mips-sde-elf-gcc: error: unrecognized argument in option '-mips32r2 -EL -msoft-float -nostdinc -fshort-double -Os -I/home/gartnerd/code/myretrobsd/include -x assembler-with-cpp -c -B/home/gartnerd/code/myretrobsd/lib/ -I/home/gartnerd/code/myretrobsd/src/libc/mips/sys -I/usr/local/mips-2013.11/mips-sde-elf/include/sys -DLWHI=lwr -DLWLO=lwl -DSWHI=swr -DSWLO=swl'
mips-sde-elf-gcc: note: valid arguments to '-mips' are: 1 2 3 32 32r2 4 64 64r2

解决方案 #

修正CMAKE_C_FLAGS定义 #

移除CFLAGS定义中的引号，让每个编译选项作为独立参数传递：

set(CMAKE_C_FLAGS -mips32r2 -EL -msoft-float -nostdinc -fshort-double -Os -I${TOPSRC}/include -x assembler-with-cpp -c -B${TOPSRC}/lib/)
set(CMAKE_C_FLAGS ${CMAKE_C_FLAGS} -I${TOPSRC}/src/libc/mips/sys -I/usr/local/mips-2013.11/mips-sde-elf/include/sys -DLWHI=lwr -DLWLO=lwl -DSWHI=swr -DSWLO=swl)

修改COMMAND行 #

去掉COMMAND中的引号，确保管道命令能正确解析每个参数：

COMMAND bash ${OBJECT_OUTPUT_DIR}/${OBJ_FILE}.sh | ${CMAKE_C_COMPILER} ${CMAKE_C_FLAGS} - -c -o ${OBJECT_OUTPUT_DIR}/${OBJ_FILE}.o 

内容的提问来源于stack exchange，提问作者Agent13