Makefile 当只指定了没有（显式）先决条件的目标时，会调用哪些make隐式规则？

我在

src

目录中有源文件

偶数\奇数\列表.c

。这是我正在试验的

makefile

VPATH = src include
CPPFLAGS = -I include

even_odd_list:

我已经调用了

make-pn

来检查所有的隐式规则，但是我没有看到一个似乎适用的规则

---

我错过了什么？请解释make正在执行的逻辑流。

make将匹配此隐式规则（通过检查

make-pf/def/null

找到）：

---

这里忽略的事实是，如何使目标与隐式规则匹配。在这种情况下，没有指定先决条件，但是如果规则的先决条件存在或应该存在并且可以生成，make将匹配隐式规则。当匹配隐式规则的先决条件存在且未指定时，将其视为隐式先决条件

因此，要匹配的第一条规则是：

%: %.c
#  commands to execute (built-in):
        $(LINK.c) $^ $(LOADLIBES) $(LDLIBS) -o $@

此页面有更多信息

使用

make-d

将显示make正在执行的步骤。以下是此示例的相关输出：

Updating goal targets....
Considering target file `even_odd_list'.
 File `even_odd_list' does not exist.
 Looking for an implicit rule for `even_odd_list'.
 Trying pattern rule with stem `even_odd_list'.
 Trying implicit prerequisite `even_odd_list.o'.
 Trying pattern rule with stem `even_odd_list'.
 Trying implicit prerequisite `even_odd_list.c'.
 Found prerequisite `even_odd_list.c' as VPATH `src/even_odd_list.c'
 Found an implicit rule for `even_odd_list'.
  Considering target file `even_odd_list.c'.
   Looking for an implicit rule for `even_odd_list.c'.
   Trying pattern rule with stem `even_odd_list'.
   Trying implicit prerequisite `even_odd_list.y'.
   Trying pattern rule with stem `even_odd_list'.
   Trying implicit prerequisite `even_odd_list.l'.
   Trying pattern rule with stem `even_odd_list'.
   Trying implicit prerequisite `even_odd_list.w'.
   Trying pattern rule with stem `even_odd_list'.
   Trying implicit prerequisite `even_odd_list.w'.
   Trying pattern rule with stem `even_odd_list.c'.
   Trying implicit prerequisite `even_odd_list.c,v'.
   Trying pattern rule with stem `even_odd_list.c'.
   Trying implicit prerequisite `RCS/even_odd_list.c,v'.
   Trying pattern rule with stem `even_odd_list.c'.
   Trying implicit prerequisite `RCS/even_odd_list.c'.
   Trying pattern rule with stem `even_odd_list.c'.
   Trying implicit prerequisite `s.even_odd_list.c'.
   Trying pattern rule with stem `even_odd_list.c'.
   Trying implicit prerequisite `SCCS/s.even_odd_list.c'.
   Trying pattern rule with stem `even_odd_list'.
   Trying implicit prerequisite `even_odd_list.y'.
   Looking for a rule with intermediate file `even_odd_list.y'.
    Avoiding implicit rule recursion.
    Trying pattern rule with stem `even_odd_list.y'.
    Trying implicit prerequisite `even_odd_list.y,v'.
    Trying pattern rule with stem `even_odd_list.y'.
    Trying implicit prerequisite `RCS/even_odd_list.y,v'.
    Trying pattern rule with stem `even_odd_list.y'.
    Trying implicit prerequisite `RCS/even_odd_list.y'.
    Trying pattern rule with stem `even_odd_list.y'.
    Trying implicit prerequisite `s.even_odd_list.y'.
    Trying pattern rule with stem `even_odd_list.y'.
    Trying implicit prerequisite `SCCS/s.even_odd_list.y'.
   Trying pattern rule with stem `even_odd_list'.
   Trying implicit prerequisite `even_odd_list.l'.
   Looking for a rule with intermediate file `even_odd_list.l'.
    Avoiding implicit rule recursion.
    Trying pattern rule with stem `even_odd_list.l'.
    Trying implicit prerequisite `even_odd_list.l,v'.
    Trying pattern rule with stem `even_odd_list.l'.
    Trying implicit prerequisite `RCS/even_odd_list.l,v'.
    Trying pattern rule with stem `even_odd_list.l'.
    Trying implicit prerequisite `RCS/even_odd_list.l'.
    Trying pattern rule with stem `even_odd_list.l'.
    Trying implicit prerequisite `s.even_odd_list.l'.
    Trying pattern rule with stem `even_odd_list.l'.
    Trying implicit prerequisite `SCCS/s.even_odd_list.l'.
   Trying pattern rule with stem `even_odd_list'.
   Trying implicit prerequisite `even_odd_list.w'.
   Looking for a rule with intermediate file `even_odd_list.w'.
    Avoiding implicit rule recursion.
    Trying pattern rule with stem `even_odd_list.w'.
    Trying implicit prerequisite `even_odd_list.w,v'.
    Trying pattern rule with stem `even_odd_list.w'.
    Trying implicit prerequisite `RCS/even_odd_list.w,v'.
    Trying pattern rule with stem `even_odd_list.w'.
    Trying implicit prerequisite `RCS/even_odd_list.w'.
    Trying pattern rule with stem `even_odd_list.w'.
    Trying implicit prerequisite `s.even_odd_list.w'.
    Trying pattern rule with stem `even_odd_list.w'.
    Trying implicit prerequisite `SCCS/s.even_odd_list.w'.
   Trying pattern rule with stem `even_odd_list'.
   Rejecting impossible implicit prerequisite `even_odd_list.w'.
   No implicit rule found for `even_odd_list.c'.
   Finished prerequisites of target file `even_odd_list.c'.
  No need to remake target `even_odd_list.c'; using VPATH name `src/even_odd_list.c'.
 Finished prerequisites of target file `even_odd_list'.
Must remake target `even_odd_list'.
cc  -I include   src/even_odd_list.c   -o even_odd_list
Putting child 0x085fbe90 (even_odd_list) PID 24853 on the chain.
Live child 0x085fbe90 (even_odd_list) PID 24853 
Reaping winning child 0x085fbe90 PID 24853 
Removing child 0x085fbe90 PID 24853 from chain.
Successfully remade target file `even_odd_list'.

---

谢谢你的回答，但我也想知道为什么。在做了更多的挖掘和检查make-d的输出之后，我开始更多地研究隐含的先决条件；你没有问其他问题。为什么？Make选择该规则是因为（a）makefile中没有为该目标定义配方，以及（b）规则中的

%

模式匹配您要构建的目标（

%

当然匹配所有内容），以及（c）该规则的先决条件

%.c

（既然

%

匹配

奇偶列表

那么

%.c

匹配

奇偶列表.c

）存在。所以make使用了这个规则。我本来可以说得更好。我正在学习一本书，书中包含了源文件作为先决条件，所以我认为这是必要的，但现在看来它是多余的。源文件是一个隐含的先决条件；这很有意义。在我发布的make文件中，我想知道目标文件如何匹配wi您指定的规则。了解隐含的先决条件似乎很清楚。如果您正在编写自己的显式规则和配方，那么您必须自己提供所有先决条件，包括

.c

文件。如果您使用的是隐式规则，则make将选择“最佳”隐式规则（确切的算法在GNU make手册中有描述）基于它可用的文件，或者知道如何构建。在这种情况下，它通常知道至少一个已经存在的先决条件，因为它在隐式规则中有描述。

Updating goal targets....
Considering target file `even_odd_list'.
 File `even_odd_list' does not exist.
 Looking for an implicit rule for `even_odd_list'.
 Trying pattern rule with stem `even_odd_list'.
 Trying implicit prerequisite `even_odd_list.o'.
 Trying pattern rule with stem `even_odd_list'.
 Trying implicit prerequisite `even_odd_list.c'.
 Found prerequisite `even_odd_list.c' as VPATH `src/even_odd_list.c'
 Found an implicit rule for `even_odd_list'.
  Considering target file `even_odd_list.c'.
   Looking for an implicit rule for `even_odd_list.c'.
   Trying pattern rule with stem `even_odd_list'.
   Trying implicit prerequisite `even_odd_list.y'.
   Trying pattern rule with stem `even_odd_list'.
   Trying implicit prerequisite `even_odd_list.l'.
   Trying pattern rule with stem `even_odd_list'.
   Trying implicit prerequisite `even_odd_list.w'.
   Trying pattern rule with stem `even_odd_list'.
   Trying implicit prerequisite `even_odd_list.w'.
   Trying pattern rule with stem `even_odd_list.c'.
   Trying implicit prerequisite `even_odd_list.c,v'.
   Trying pattern rule with stem `even_odd_list.c'.
   Trying implicit prerequisite `RCS/even_odd_list.c,v'.
   Trying pattern rule with stem `even_odd_list.c'.
   Trying implicit prerequisite `RCS/even_odd_list.c'.
   Trying pattern rule with stem `even_odd_list.c'.
   Trying implicit prerequisite `s.even_odd_list.c'.
   Trying pattern rule with stem `even_odd_list.c'.
   Trying implicit prerequisite `SCCS/s.even_odd_list.c'.
   Trying pattern rule with stem `even_odd_list'.
   Trying implicit prerequisite `even_odd_list.y'.
   Looking for a rule with intermediate file `even_odd_list.y'.
    Avoiding implicit rule recursion.
    Trying pattern rule with stem `even_odd_list.y'.
    Trying implicit prerequisite `even_odd_list.y,v'.
    Trying pattern rule with stem `even_odd_list.y'.
    Trying implicit prerequisite `RCS/even_odd_list.y,v'.
    Trying pattern rule with stem `even_odd_list.y'.
    Trying implicit prerequisite `RCS/even_odd_list.y'.
    Trying pattern rule with stem `even_odd_list.y'.
    Trying implicit prerequisite `s.even_odd_list.y'.
    Trying pattern rule with stem `even_odd_list.y'.
    Trying implicit prerequisite `SCCS/s.even_odd_list.y'.
   Trying pattern rule with stem `even_odd_list'.
   Trying implicit prerequisite `even_odd_list.l'.
   Looking for a rule with intermediate file `even_odd_list.l'.
    Avoiding implicit rule recursion.
    Trying pattern rule with stem `even_odd_list.l'.
    Trying implicit prerequisite `even_odd_list.l,v'.
    Trying pattern rule with stem `even_odd_list.l'.
    Trying implicit prerequisite `RCS/even_odd_list.l,v'.
    Trying pattern rule with stem `even_odd_list.l'.
    Trying implicit prerequisite `RCS/even_odd_list.l'.
    Trying pattern rule with stem `even_odd_list.l'.
    Trying implicit prerequisite `s.even_odd_list.l'.
    Trying pattern rule with stem `even_odd_list.l'.
    Trying implicit prerequisite `SCCS/s.even_odd_list.l'.
   Trying pattern rule with stem `even_odd_list'.
   Trying implicit prerequisite `even_odd_list.w'.
   Looking for a rule with intermediate file `even_odd_list.w'.
    Avoiding implicit rule recursion.
    Trying pattern rule with stem `even_odd_list.w'.
    Trying implicit prerequisite `even_odd_list.w,v'.
    Trying pattern rule with stem `even_odd_list.w'.
    Trying implicit prerequisite `RCS/even_odd_list.w,v'.
    Trying pattern rule with stem `even_odd_list.w'.
    Trying implicit prerequisite `RCS/even_odd_list.w'.
    Trying pattern rule with stem `even_odd_list.w'.
    Trying implicit prerequisite `s.even_odd_list.w'.
    Trying pattern rule with stem `even_odd_list.w'.
    Trying implicit prerequisite `SCCS/s.even_odd_list.w'.
   Trying pattern rule with stem `even_odd_list'.
   Rejecting impossible implicit prerequisite `even_odd_list.w'.
   No implicit rule found for `even_odd_list.c'.
   Finished prerequisites of target file `even_odd_list.c'.
  No need to remake target `even_odd_list.c'; using VPATH name `src/even_odd_list.c'.
 Finished prerequisites of target file `even_odd_list'.
Must remake target `even_odd_list'.
cc  -I include   src/even_odd_list.c   -o even_odd_list
Putting child 0x085fbe90 (even_odd_list) PID 24853 on the chain.
Live child 0x085fbe90 (even_odd_list) PID 24853 
Reaping winning child 0x085fbe90 PID 24853 
Removing child 0x085fbe90 PID 24853 from chain.
Successfully remade target file `even_odd_list'.