makefile if string not empty
The result is that `CC=gcc' as an argument to make changes not only which compiler is used ... Often you want to test if a variable has a non-empty value. ... However, you can use the strip function (see section Functions for String Substitution ,Conditional Syntax (GNU make) ... The syntax of a simple conditional with no else is as follows: ... Often you want to test if a variable has a non-empty value. , To expand the CXX variable in Makefile, the preferred syntax is to use ... means "if $(CXXARCH) does not expand to an empty string, then..."., Note that there are no TABs preceding ifeq and endif ; those are not ... unless you actually intend that the variable should contain the string ' ""'., Makefile ENVIRONMENT ?= development ifeq ($(filter $(ENVIRONMENT) ... See 8.2 Functions for String Substitution and Analysis., This reflects the behavior of the ifndef conditional, so that a variable defined to an empty value is also considered "undefined". But this is only ..., which will replace all quotes with nothing; if the result of that is an empty string then you know the variables were either empty or contained ..., As your MY_VAR variable is used only in recipes, is target-dependent and you want it to be computed only when needed, why don't you use ..., Makefile set if variable is empty. The first $(something) may return an empty string, however the conditional assignment ?= works only if the previous variable is not set, not if empty.
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 makefile if string not empty 相關參考資料
GNU make - Conditional Parts of Makefiles
The result is that `CC=gcc' as an argument to make changes not only which compiler is used ... Often you want to test if a variable has a non-empty value. ... However, you can use the strip functi... ftp://ftp.gnu.org Conditional Syntax (GNU make)
Conditional Syntax (GNU make) ... The syntax of a simple conditional with no else is as follows: ... Often you want to test if a variable has a non-empty value. https://www.gnu.org Check if a command returns nothing in Makefile - Stack Overflow
To expand the CXX variable in Makefile, the preferred syntax is to use ... means "if $(CXXARCH) does not expand to an empty string, then...". https://stackoverflow.com makefile: fail on single make target if variable empty - Stack ...
Note that there are no TABs preceding ifeq and endif ; those are not ... unless you actually intend that the variable should contain the string ' ""'. https://stackoverflow.com Makefile - How to check if variable is not empty and is one of the ...
Makefile ENVIRONMENT ?= development ifeq ($(filter $(ENVIRONMENT) ... See 8.2 Functions for String Substitution and Analysis. https://stackoverflow.com Abort makefile if variable not set - Stack Overflow
This reflects the behavior of the ifndef conditional, so that a variable defined to an empty value is also considered "undefined". But this is only ... https://stackoverflow.com Null check and empty string check in makefile - Stack Overflow
which will replace all quotes with nothing; if the result of that is an empty string then you know the variables were either empty or contained ... https://stackoverflow.com Makefile test if variable is not empty - Stack Overflow
As your MY_VAR variable is used only in recipes, is target-dependent and you want it to be computed only when needed, why don't you use ... https://stackoverflow.com Makefile set if variable is empty - Stack Overflow
Makefile set if variable is empty. The first $(something) may return an empty string, however the conditional assignment ?= works only if the previous variable is not set, not if empty. https://stackoverflow.com |