.if and Makefile issues

[Don Lewis]

On 25 Mar, Don Lewis wrote:
> On 25 Mar, Gary Aitken wrote:
>> Bewildered and frustrated, looking for some guidance on a seemingly
>> simple task: check the existence of a file and rename it.
>> 
>> Looking at a number of examples in the Porter's guide, I should be
>> able to do something like this:
>> 
>> post-build:
>> <ht>echo "***** post-build *****"
>> #<ht>Avoid executable name conflict with dcraw port
>> <ht>.if exists ${WRKSRC}/dcraw
>> <ht>echo ===== dcraw exists =====
>> <ht>mv ${WRKSRC}/dcraw ${WRKSRC}/${PORTNAME}-dcraw
>> <ht>.else
>> <ht>echo ===== dcraw does not exist =====
>> <ht>.endif
>> 
>> That causes:
>> echo "***** post-build *****"
>> ***** post-build *****
>> .if exists /usr/ports/graphics/ufraw-devel/work/ufraw-6d3259a/dcraw
>> make[1]: exec(.if) failed (No such file or directory)
>> *** Error code 1
> 
> Since the .if is indented, it is being treated as a shell command,
> and .if isn't being found in $PATH.
> 
>> I then tried adding parens:
>> 
>> post-build:
>> <ht>echo "***** post-build *****"
>> #<ht>Avoid executable name conflict with dcraw port
>> <ht>.if exists(${WRKSRC}/dcraw)
>> <ht>echo "===== dcraw exists ====="
>> <ht>mv ${WRKSRC}/dcraw ${WRKSRC}/${PORTNAME}-dcraw
>> <ht>.else
>> <ht>echo "===== dcraw does not exist ====="
>> <ht>.endif
>> 
>> echo "***** post-build *****"
>> ***** post-build *****
>> .if exists(/usr/ports/graphics/ufraw-devel/work/ufraw-6d3259a/dcraw)
>> Syntax error: "(" unexpected
>> *** Error code 2
> 
> Ditto, but the shell command has a shell syntax error.
>  
>> I finally got this to do *something*:
>> 
>> post-build:
>> <ht>echo "***** post-build *****"
>> #   Avoid executable name conflict with dcraw port
>> .if exists ${WRKSRC}/dcraw
>> echo ===== dcraw exists =====
>> mv ${WRKSRC}/dcraw ${WRKSRC}/${PORTNAME}-dcraw
>> .else
>> <ht>echo ===== dcraw does not exist =====
>> .endif
>> 
>> echo "***** post-build *****"
>> ***** post-build *****
>> echo "===== dcraw does not exist ====="
>> ===== dcraw does not exist =====
>> 
>> Unfortunately, the file *does* exist.
> 
> The .if is treated as a make directive in this case, but it is
> evaluated at the time that make is first invoked, probably when
> when "make build" is first executed, or earlier.
> 
>> Can someone enlighten me as to what is going on in the above three
>> situations, to further my education?
>> Any hints / pointers would be much appreciated:
>> 
>> 1. Why does the .if, .else, and .endif have to have no leading whitespace?
> 
> If there is leading whitespace, then make assumes they are shell
> commands.
> 
>> 2. Why does it require the <ht> on the stmt after the else but not
>>     after the .if?  (Same behavior with tabs on the ones after .if)
> 
> Probably because the .if evaluates false, so anything between the .if
> and the .else isn't even parsed.
> 
>> 3. Why doesn't it find the file?
> 
> Because the file doesn't exist when the make first parses the Makefile.
> 
>> 4. What's a right way to do this?
> 
> Use a shell runtime test:
> 
> post-build:
> <ht>echo "***** post-build *****"
> <ht>#   Avoid executable name conflict with dcraw port
> <ht>if [ -e ${WRKSRC}/dcraw ]; then
> <ht><ht>echo ===== dcraw exists =====
> <ht><ht>mv ${WRKSRC}/dcraw ${WRKSRC}/${PORTNAME}-dcraw
> <ht>else
> <ht><ht>echo ===== dcraw does not exist =====
> <ht>fi

I forgot that all of the lines from the "if" up to but not including
"fi" need to end with a \ so that make treats them all as one multi-line
shell command:

post-build:
<ht>echo "***** post-build *****"
<ht>#   Avoid executable name conflict with dcraw port
<ht>if [ -e ${WRKSRC}/dcraw ]; then \
<ht><ht>echo ===== dcraw exists ===== \
<ht><ht>mv ${WRKSRC}/dcraw ${WRKSRC}/${PORTNAME}-dcraw \
<ht>else \
<ht><ht>echo ===== dcraw does not exist ===== \
<ht>fi