GNU Make - 对非程序代码的依赖

发布于 2024-09-02 23:22:15 字数 681 浏览 7 评论 0原文

我正在编写的程序的一个要求是它必须能够信任配置文件。为了实现这一点，我使用多种哈希算法在编译时生成文件的哈希值，这会生成一个以哈希值作为常量的标头。

其依赖关系非常简单，我的程序依赖于 config_hash.h，它有一个生成它的目标。

makefile 看起来像这样：

config_hash.h:
    $(SH) genhash config/config_file.cfg > $(srcdir)/config_hash.h

$(PROGRAM): config_hash.h $(PROGRAM_DEPS)
    $(CC) ... ... ...

我正在使用 gcc 的 -M 选项，这对于处理依赖关系非常有用。如果我的标题发生变化，我的程序就会重建。

我的问题是，我需要能够判断配置文件是否已更改，以便重新生成 config_hash.h。我不太确定如何解释这种对 GNU make 的依赖。

我尝试将 config/config_file.cfg 列为 config_hash.h 的依赖项，并为 config_file.cfg 提供 .PHONY 目标，但没有成功。显然，我不能依赖 gcc 的 -M 开关来帮助我，因为配置文件不是任何目标代码的一部分。

有什么建议吗？不幸的是，我不能发布大部分 Makefile，否则我就会发布整个内容。

原文

A requirement for a program I am writing is that it must be able to trust a configuration file. To accomplish this, I am using several kinds of hashing algorithms to generate a hash of the file at compile time, this produces a header with the hashes as constants.

Dependencies for this are pretty straight forward, my program depends on config_hash.h, which has a target that produces it.

The makefile looks something like this :

config_hash.h:
    $(SH) genhash config/config_file.cfg > $(srcdir)/config_hash.h

$(PROGRAM): config_hash.h $(PROGRAM_DEPS)
    $(CC) ... ... ...

I'm using the -M option to gcc, which is great for dealing with dependencies. If my header changes, my program is rebuilt.

My problem is, I need to be able to tell if the config file has changed, so that config_hash.h is re-generated. I'm not quite sure how explain that kind of dependency to GNU make.

I've tried listing config/config_file.cfg as a dependency for config_hash.h, and providing a .PHONY target for config_file.cfg without success. Obviously, I can't rely on the -M switch to gcc to help me here, since the config file is not a part of any object code.

Any suggestions? Unfortunately, I can't post much of the Makefile, or I would have just posted the whole thing.

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救赎№ 2024-09-09 23:22:16

在 .PHONY 中声明文件是错误的。那里列出的任何依赖项都不会在文件系统中进行检查。只需将其列为哈希标头的依赖项并从那里开始即可。

回复收藏 0 原文

静谧幽蓝 2024-09-09 23:22:16

当您将 config/config_file.cfg 添加到 config_hash.h 的依赖项时发生了什么，为什么它不是您所期望的？

类似的规则

config_hash.h:config/config_file.cfg
    $(SH) genhash lt; > $@

如果 config/config_file.cfg 较新，则将重新生成 config_hash.h。然后，您的 gcc 生成的依赖项将根据 config_hash.h 重新编译任何内容。

$@ 变量是目标，使用它可确保您正在创建所需的文件（在您的问题中，如果定义了 srcdir ，则规则表示它将生成 ./config_hash.h，但实际上会创建./$(srcdir)/config_hash.h)。类似地，$< 和 $^ 分别给出第一个和所有先决条件。

我假设你有一个像这样的makefile

CPPFLAGS+=-MMD -MP
all:
# etc.
config_hash.h:config/config_file.cfg
    $(SH) genhash lt; > $@
%.d %.o:%.c
    $(CC) $(CPPFLAGS) $(CFLAGS) -c -o $*.o lt;
%.d %.o:%.cpp
    $(CXX) $(CPPFLAGS) $(CXXFLAGS) -c -o $*.o lt;
-include $(wildcard *.d) /dev/null

What happened when you added config/config_file.cfg to the dependancies of config_hash.h, and why wasn't it what you expected?

A rule like

config_hash.h:config/config_file.cfg
    $(SH) genhash lt; > $@

would regenerate config_hash.h if config/config_file.cfg was more recent. Your gcc generated dependancies would then recompile anything depending on config_hash.h.

The $@ variable is the target, using this ensures you are creating the file you asked for (In your question, if srcdir is defined the rule says it will generate ./config_hash.h, but will actually create ./$(srcdir)/config_hash.h). Similarly $< and $^ give the first and all prerequisites respectively.

I'm assuming you have a makefile like

CPPFLAGS+=-MMD -MP
all:
# etc.
config_hash.h:config/config_file.cfg
    $(SH) genhash lt; > $@
%.d %.o:%.c
    $(CC) $(CPPFLAGS) $(CFLAGS) -c -o $*.o lt;
%.d %.o:%.cpp
    $(CXX) $(CPPFLAGS) $(CXXFLAGS) -c -o $*.o lt;
-include $(wildcard *.d) /dev/null

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~没有更多了~