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Text Functions
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File Name Functions
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File Function
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Origin Function
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Flavor Function
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<h1 id="conditional-directives">Conditional Directives</h1>
<p>조건 지시자는 C/C++ 언어의 전처리기 에서처럼 특정 코드를 조건에 따라 포함하거나 제외하고자 할 때
사용합니다.
makefile 의 모든 부분에서 적용할 수 있으나 recipe 가 실행되기 전에 처리가 완료되므로
recipe 실행 중에 처리를 위해서는 사용할 수 없습니다.
기본적으로 <code>ifxxxx ~ else ~ endif</code> 형식을 가지는데 <code>else</code> 지시자는 옵션으로
사용되지 않을 경우 제외할 수 있습니다.</p>
<blockquote>
<p>recipe 실행 중에 automatic 변수와 함께 조건문을 사용하려면 <a href="builtin_functions/conditional_functions.html">Conditional built-in 함수</a>를 사용합니다.</p>
</blockquote>
<h4 id="ifeq--ifneq----else----endif">ifeq , ifneq . . . else . . . endif</h4>
<p>값 비교에는 다음과 같은 3 가지 형식을 사용할 수 있습니다.
quotes 을 사용하는 형식은 quotes 이 중첩될 경우 오류가 발생할 수 있으므로 주의해야 합니다.</p>
<pre><code class="lang-makefile">ifeq (arg1,arg2) ifneq (arg1,arg2)
ifeq "a" "b" ifneq "a" "b"
ifeq 'a' 'b' ifneq 'a' 'b'
-------------------------------------------------
<span class="hljs-comment"># shell 함수에서 사용하는 quotes 과 중첩되어 오류가 발생한다.</span>
ifeq "$(shell echo "foo bar")" "foo bar"
$(info 11111 )
endif
실행결과: Makefile:1: *** unterminated call to function 'shell': missing ')'. Stop.
<span class="hljs-comment"># 이때는 괄호형을 사용하거나 변수에 대입해서 사용하면 됩니다.</span>
ifeq ($(shell echo "foo bar"),foo bar)
$(info 11111 )
endif
실행결과: 11111
</code></pre>
<p><code>( )</code> 괄호형을 사용할 때는 가운데 공백은 값에 포함되지 않지만
양끝에 공백은 값에 포함되므로 주의해야 합니다.
따라서 다음 세 번째 예제의 경우 실제 값은 <code>" foo"</code> 와 <code>"foo "</code> 가 되어 거짓이 됩니다.</p>
<pre><code class="lang-makefile">$ make -f- <<\@ $ make -f- <<\@ $ make -f- <<\@
ifeq (foo,foo) ifeq (foo , foo) ifeq ( foo,foo )
$(info equal) $(info equal) $(info equal)
else else else
$(info not equal) $(info not equal) $(info not equal)
endif endif endif
@ @ @
equal equal not equal
</code></pre>
<h4 id="ifdef--ifndef----else----endif">ifdef , ifndef . . . else . . . endif</h4>
<p><code>ifdef</code>, <code>ifndef</code> 지시자는 flavor, origin 함수에서 사용되는
undefined 상태를 체크하는 것이 아니고 값이 empty 인지 아닌지를 체크합니다.
따라서 변수가 존재하나 값이 empty 일 경우와 undefined 상태일 경우
모두 <code>ifndef</code> 에서는 참이 됩니다.</p>
<pre><code class="lang-makefile">ifdef variable ifndef variable
--------------------------------------------------------
<span class="hljs-constant">AA</span> :=
ifndef AA <span class="hljs-comment"># 변수가 존재하지만 empty 이므로 참이된다.</span>
$(info AA is not defined or empty )
endif
<span class="hljs-comment">####### 실행 결과 ######</span>
AA is not defined or empty
</code></pre>
<h4 id="and--or-연산">and , or 연산</h4>
<p>조건 지시자에는 기본적으로 and, or 연산자가 없습니다.
따라서 다음과 같이 사용해야 합니다.</p>
<pre><code class="lang-makefile">
ifeq (arg1,arg2) ---- (1)
ifeq (arg1,arg2) ---- (2)
<span class="hljs-comment"># (1) and (2) 가 참이면 실행</span>
endif
endif
----------------------------------------
ifeq (arg1,arg2) ---- (1)
<span class="hljs-comment"># (1) 이 참이면 실행</span>
else ifeq (arg1,arg2) ---- (2)
<span class="hljs-comment"># (1) 이 거짓이고 (2) 는 참이면 실행</span>
else
<span class="hljs-comment"># (1), (2) 모두 거짓이면 실행</span>
endif
</code></pre>
<h4 id="strip-함수의-사용">strip 함수의 사용</h4>
<p><code>if</code> 함수의 condition 부분이 아닌 반환값에 사용되는 then, else 파트 부분에서는
공백도 하나의 값으로 인식됩니다. 따라서 <code>\</code> 문자를 이용해 개행을 해서 작성할때는
반드시 <code>strip</code> 함수를 사용해야 합니다.</p>
<pre><code class="lang-bash">aa := foo aa := foo
bb := bb :=
<span class="hljs-comment"># strip 함수 사용 </span>
ifneq <span class="hljs-string">"<span class="hljs-variable">$(if $(aa)</span>, <span class="hljs-variable">$(bb)</span>)"</span> <span class="hljs-string">""</span> ifneq <span class="hljs-string">"<span class="hljs-variable">$(strip $(if $(aa)</span>, <span class="hljs-variable">$(bb)</span>))"</span> <span class="hljs-string">""</span>
$(info <span class="hljs-number">1111111111</span>) $(info <span class="hljs-number">1111111111</span>)
endif endif
<span class="hljs-comment">####### 실행 결과 ####### ####### 실행 결과 #######</span>
$ make $ make
<span class="hljs-number">1111111111</span> $
------------------------------------------------------------------------------
<span class="hljs-comment"># if 함수의 then, else 파트 부분에 공백이 있어서 ifneq 조건 지시자는 무조건 참이 된다.</span>
ifneq <span class="hljs-string">"<span class="hljs-variable">$(if $(MAKECMDGOALS)</span>, \
<span class="hljs-variable">$(filter all clean all.% clean.%,$(MAKECMDGOALS)</span>), \
<span class="hljs-variable">$(filter all clean all.% clean.%,$(.DEFAULT_GOAL)</span>))"</span> <span class="hljs-string">""</span>
<span class="hljs-comment"># 값으로 인식되는 공백을 제거하기 위해 strip 함수를 사용해야 한다.</span>
ifneq <span class="hljs-string">"<span class="hljs-variable">$(strip $(if $(MAKECMDGOALS)</span>, \
<span class="hljs-variable">$(filter all clean all.% clean.%,$(MAKECMDGOALS)</span>), \
<span class="hljs-variable">$(filter all clean all.% clean.%,$(.DEFAULT_GOAL)</span>)))"</span> <span class="hljs-string">""</span>
</code></pre>
<h4 id="사용-예제-">사용 예제 )</h4>
<p>1 . recipe 에서 사용할 경우</p>
<pre><code class="lang-makefile"><span class="hljs-comment"># recipe 에서 실행되므로 shell 명령을 작성할 때는 앞에 tab 문자를 붙입니다.</span>
prog : $(OBJS)
ifeq "$(MYVAR)" "foo"
$(CC) $+ $(libs_for_foo) -o $@ <span class="hljs-comment"># tab</span>
else
$(CC) $+ $(normal_libs) -o $@
endif
</code></pre>
<p>2 . global 영역에서 사용할 경우</p>
<pre><code class="lang-makefile">ifeq "$(MYVAR)" "foo"
prog : foo.o bar.o zoo.o
$(CC) $+ -o $@
else
prog : xxx.o yyy.o zzz.o
$(CC) $+ -o $@
endif
</code></pre>
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