Makefile ifeq logical or

Question

How do you perform a logical OR using make s ifeq operator   e g   I have  simplified    ifeq    GCC MINOR   4      CFLAGS    -fno-strict-overflow endif ifeq    GCC MINOR   5      CFLAGS    -fno-strict-overflow endif   but would like to consolidate these lines    yes  yes  autotools  configure  etc etc  too heavy-handed for the current situation  would like to keep everything within the Makefile here    logical opposite of this question  How to Use of Multiple condition in   39 ifeq  39  statement

User · Accepted Answer

As found on the mailing list archive   http   osdir com ml gnu make windows 2004-03 msg00063 html http   osdir com ml gnu make general 2005-10 msg00064 html  one can use the filter function  For example ifeq    GCC MINOR    filter   GCC MINOR  4 5    filter X  A B will return those of A B that are equal to X  Note  while this is not relevant in the above example  this is a XOR operation  I e  if you instead have something like  ifeq  4    filter 4    VAR1    VAR2     And then do e g  make VAR1 4 VAR2 4  the filter will return 4 4  which is not equal to 4  A variation that performs an OR operation instead is  ifneq     filter   GCC MINOR  4 5    where a negative comparison against an empty string is used instead  filter will return en empty string if GCC MINOR doesn t match the arguments   Using the VAR1 VAR2 example it would look like this  ifneq      filter 4    VAR1    VAR2     The downside to those methods is that you have to be sure that these arguments will always be single words  For example  if VAR1 is 4 foo  the filter result is still 4  and the ifneq expression is still true  If VAR1 is 4 5  the filter result is 4 5 and the ifneq expression is true  One easy alternative is to just put the same operation in both the ifeq and else ifeq branch  e g  like this  ifeq    GCC MINOR  4       echo Supported version else ifeq    GCC MINOR  5       echo Supported version else      echo Unsupported version endif

User · Answer

You can introduce another variable   It doesnt consolidate both checks  but it at least avoids having to put the body in twice   do it    ifeq    GCC MINOR   4      do it   yes endif ifeq    GCC MINOR   5      do it   yes endif ifdef do it     CFLAGS    -fno-strict-overflow endif

User · Answer

I don t think there s a concise  sensible way to do that  but there are verbose  sensible ways  such as Foo Bah s  and concise  pathological ways  such as  ifneq     findstring   GCC MINOR  4-5       CFLAGS    -fno-strict-overflow endif    which will execute the command provided that the string   GCC MINOR  appears inside the string 4-5

User · Answer

ifeq    GCC MINOR   4      CFLAGS    -fno-strict-overflow endif ifeq    GCC MINOR   5      CFLAGS    -fno-strict-overflow endif    Another you can consider using in this case is   GCC42 OR LATER     shell   CXX  -v 2 gt  amp 1     EGREP  -c   gcc version  4  2-9   5-9        -Wstrict-overflow  http   www airs com blog archives 120 ifeq    GCC42 OR LATER  1    CFLAGS    -Wstrict-overflow endif   I actually use the same in my code because I don t want to maintain a separate config or Configure   But you have to use a portable  non-anemic make  like GNU make  gmake   and not Posix s make   And it does not address the issue of logical AND and OR

User · Answer

Here more flexible variant  it uses external shell  but allows to check for arbitrary conditions   ifeq    shell test     GCC MINOR      4  -o                           GCC MINOR      5  -o                           TODAY          Friday   amp  amp   printf  true    true      CFLAGS    -fno-strict-overflow endif

[makefile] Makefile ifeq logical or

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