58

I have a C++ preprocessor written like this:

  #ifdef cpp_variable
   //x+y;
  #endif

Can anyone tell me how to define this in Makefile.

vikrant rana
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Joel
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6 Answers6

56

This is compiler specific.

GCC uses -Dcpp_variable=VALUE or just -Dcpp_variable

Microsoft's compilers use /D

Itay Grudev
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Reed Copsey
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37

Search your compiler documentation to find how to do that.

For example for g++ the syntax is :

g++ -Dcpp_variable <other stuff>

Which corresponds to adding

CPPFLAGS += -Dcpp_variable

in your makefile.

eddi
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fouronnes
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    Technically, because you can do it from the commandline, it can be done from the makefile -- just put the relevant command in the makefile. (pedantry aside, this comment may not have actually been correct when this answer was written) – Nic May 09 '16 at 12:47
12

Add to Makefile:

CPPFLAGS = -Dcpp_variable
Peter Tseng
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5

The syntax is compiler specific, for gcc use the -D option like so: -Dcpp_variable.

Eugen Constantin Dinca
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4

Take a variable in Makefile and whatever you need to define in it just add -DXXX. Where XXX in you case is cpp_variable.

For example

COMPILE_OPTS = -DXXX

g++ -c $(COMPILE_OPTS) $<

Akhil Pathania
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0

if you want to do below in c/cpp file

#define VARIABLE_NAME 2

then, in make file, use below lines:

CDEFS += -DVARIABLE_NAME = 2
Pawan Kumar
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