我的Makefile在BSD make报错但GNU make正常，如何实现兼容？

问题描述 #

我的Makefile在GNU make环境下可正常编译运行，但在BSD make中执行时报错：

bmake: don't know how to make .force_rebuild. Stop

希望调整Makefile以兼容BSD make，目前暂无移植计划，但预留未来兼容空间。

原Makefile内容 #

# Use the latest version of the compiler on Debian 12 OS, arm64 platform:
CXX=g++-12

# Use the official standard;
# Optimize for speed;
# Stop on all warnings;
# Do not include debug symbols:
CXXFLAGS=-std=c++17 -O3 -Wall -Wextra -Werror -Wpedantic -pedantic-errors

# The name of the resulting executable file:
APP_NAME=auto-fan-control

# The name of the C++ source code file:
SRC_FILE=$(APP_NAME).cpp

# Possibly not doing anything when using GNU make;
# You may see this for an explanation:
# https://www.gnu.org/software/make/manual/html_node/Special-Targets.html#index-POSIX_002dconforming-mode_002c-setting
.POSIX:

# You may see this for an explanation:
# https://stackoverflow.com/a/70199176/1997354
# Force re-build work-around:
.PHONY: .force_rebuild
$(APP_NAME): .force_rebuild

$(APP_NAME): $(SRC_FILE)
    @printf '%s' 'Compiling...'
    @$(CXX) $(CXXFLAGS) $(SRC_FILE) -o $(APP_NAME)
    @printf '%s\n' ' Done.'
    @strip -s $(APP_NAME)
    @printf '%s\n' 'Running program... '
    @./$(APP_NAME)

测试环境（GNU make） #

$ apt-cache policy make
make:
  Installed: 4.3-4.1build2
  Candidate: 4.3-4.1build2
  Version table:
 *** 4.3-4.1build2 500
        500 https://archive.ubuntu.com/ubuntu noble/main amd64 Packages
        100 /var/lib/dpkg/status

GNU make下运行结果 #

$ learn-cpp 
/home/vlastimil/Development/cpp/rpi4-temperature-moninor--and-fan-control
$ make
Compiling... Done.
Running program... 
25.0°C

问题原因与修复 #

错误原因 #

GNU make允许标记为.PHONY的伪目标没有对应的规则定义，默认认为该目标始终需要更新；但BSD make对.PHONY目标的处理更严格，若伪目标没有对应的规则（哪怕是空规则），会尝试查找实际文件或可执行构建规则，找不到就会报错。

兼容修改方案 #

给.force_rebuild伪目标添加一个空规则，同时将目标的依赖合并为一个规则（提升兼容性）。修改后的Makefile如下：

# Use the latest version of the compiler on Debian 12 OS, arm64 platform:
CXX=g++-12

# Use the official standard;
# Optimize for speed;
# Stop on all warnings;
# Do not include debug symbols:
CXXFLAGS=-std=c++17 -O3 -Wall -Wextra -Werror -Wpedantic -pedantic-errors

# The name of the resulting executable file:
APP_NAME=auto-fan-control

# The name of the C++ source code file:
SRC_FILE=$(APP_NAME).cpp

.POSIX:

# Force re-build work-around, compatible with GNU make and BSD make
.PHONY: .force_rebuild
.force_rebuild:

# Combine dependencies into one rule for better compatibility
$(APP_NAME): .force_rebuild $(SRC_FILE)
    @printf '%s' 'Compiling...'
    @$(CXX) $(CXXFLAGS) $(SRC_FILE) -o $(APP_NAME)
    @printf '%s\n' ' Done.'
    @strip -s $(APP_NAME)
    @printf '%s\n' 'Running program... '
    @./$(APP_NAME)

修改说明 #

1. 给.force_rebuild添加空规则：.force_rebuild:，让BSD make能识别该目标的构建规则（空操作），同时不影响GNU make的行为。
2. 将原有的两个$(APP_NAME)规则合并为一个，显式声明所有依赖，避免不同make工具对多规则依赖合并的处理差异。

修改后，Makefile即可同时在GNU make和BSD make环境下正常运行。

内容的提问来源于stack exchange，提问作者Vlastimil Burián