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using variables for paths in project file

  • Hi all -

    I have a project that relies heavily on a third-party IDF. I have many entries in my .pro file pointing to subdirectories of this IDF, like so:

    	"C:\esp-idf-release-v3.2\components\bt\include" \
    	"C:\esp-idf-release-v3.2\components\bt\bluedroid\api\include\api" \
    	"C:\esp-idf-release-v3.2\components\coap\port\include" \
    	"C:\esp-idf-release-v3.2\components\console" \
    	"C:\esp-idf-release-v3.2\components\driver\include" \
    	"C:\esp-idf-release-v3.2\components\esp_adc_cal\include" \
    	"C:\esp-idf-release-v3.2\components\esp32\include" \
    	"C:\esp-idf-release-v3.2\components\esp_https_ota\include" \

    The root directory of this IDF changes, and I'd like to use a variable (Qt or Windows) to hold it, so my .pro file would look something like:

    $IDF_PATH"\components\bt\include" \

    But I don't know the correct syntax. Couldn't find it on the QMake variables page. Can someone show me the light?


  • Lifetime Qt Champion


    Is IDF_PATH an environment variable ?

  • It certainly could be, or I could create it within Qt. Either way is fine with me.

  • Lifetime Qt Champion

    To get the content of a variable you should use: $$VARIABLE_NAME and it's an environment variable use $${ENV_VAR_NAME}.

  • That much I understand. Now, how do I fit that prefix to the rest of the path? Meaning, something like this (but this doesn't work):

    $$IDFPATH + "\components\bt\include"

  • Lifetime Qt Champion

    INCLUDEPATH += $$IDFPATH/components/bt/include

    You can (and should) use forward slash also on Windows. qmake will do the necessary conversions for you.

  • Lifetime Qt Champion


    I'd say you must ;)

    And a hint to @mzimmers: never end a line with a backslash or a slash - this will lead to problems sooner or later. I have had big problems already when doing something like: INCLUDEPATH += $$IDFPATH/components/bt/include/ as the last slash was converted to backslash and there to problems begun...

  • Yeah, I was just being lazy...I'd grabbed those paths from somewhere else and just plugged them in verbatim. Now corrected.

    So, aha - if I can't end a line with a backslash, when I want to use one as a concatenator, should I move it to the start of the next line?

    Thanks, guys.

  • Lifetime Qt Champion

    @mzimmers said in using variables for paths in project file:

    when I want to use one as a concatenator,

    You don't want to.

    A backslash at the end-of-line in a .pro file is always line-continuation. But forward slashes may be translated in the generated Makefile and that's where the fun begins...

  • Lifetime Qt Champion

    MYPATH = /usr/include

    If you need backslashes then you have to double them as you would in a classic C string. However, you really should use forward slashes.

  • @aha_1980 I misspoke - I didn't mean concatenator; I meant line continuator. I interpreted your earlier statement as saying a backslash shouldn't end a line, but I guess you meant when used as part of a Windows-style path?

  • Lifetime Qt Champion

    Hi @mzimmers,

    you're right, the backslash is the line continuator for qmake.

    but I guess you meant when used as part of a Windows-style path?

    Also correct.

    But what could be unexpected, is if you end a Unix-style path with '/', this will be converted to a backslash in the Makefile an can lead to fun there also.

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