gnu make conditional in recipe

 

 

 

 

In the next release of GNU make, for performance reasons, we may remove that sorting. New special variable: .RECIPEPREFIX allows you to reset the recipe introduction character from the The else conditional line can now be followed by any other valid conditional on the same line: this The following example of a conditional tells make to use one set of libraries if the CC variable is gcc, and a different set of libraries otherwise. It works by controlling which of two command lines will be used as the command for a rule. A conditional expression (ifdef, ifeq, etc. see Syntax of Conditionals) in a rule context which is indented by a tab as the first character on the line, will be considered part of a recipe and be passed to the shell. So you cant declare make variables or use make conditionals. 5 Writing Recipes in Rules. 6 How to Use Variables. 7 Conditional Parts of Makefiles. 8 Functions for Transforming Text.11 Using make to Update Archive Files. 12 Features of GNU make. 13 Incompatibilities and Missing Features. 14 Makefile Conventions. Next: Conditionals, Previous: Recipes, Up: Top [Contents][Index]. 6 How to Use Variables.There are two ways that a variable in GNU make can have a value we call them the two flavors of variables.

The following example of a conditional tells make to use one set of libraries if the CC variable is gcc, and a different set of libraries otherwise. It works by controlling which of two command lines will be used as the command for a rule. Undefined Variables in Conditionals.GNU make has no way of detecting that some targets ought to be rebuilt, because it doesnt take into account any change to the commands in recipes. However, the GNU Make since version 3.82 allows to choose any symbol (one character) as the recipe prefix using the .RECIPEPREFIX special variable.provides support for conditional expansion in a functional context. (or condition1[,condition2[,condition3]]) (if condition,then-part[,else-part]). The if function provides support for conditional expansion in a functional context (as opposed to the GNU make makefile conditionals such as ifeq (see Syntax of Conditionals). GNU make 1 Overview of make 2 An Introduction to Makefiles 3 Writing Makefiles 4 Writing Rules 5 Writing Recipes in Rules 6 How to Use Variables 7 Conditional Parts of Makefiles 8Splitting Lines: Breaking long recipe lines for readability. Variables in Recipes: Using make variables in recipes.

1. I am using gnu make and in a Makefile I have, I see below rule. I want to add a similar rule with a recipe, but when I add a rule and its receipe on the next line by giving a tab or space for the recipe, I get make error.Conditional variables in Makefile. 0. make evaluates conditionals when it reads a makefile. Consequently, you cannot use automatic variables in the tests of conditionals because they are not defined until recipes are run (see Automatic Variables). See Section 5. A conditional expression (ifdef.1 Splitting Recipe Lines One of the few ways in which make does interpret recipes is checking for a backslash justwill not be visible in any recipe.14 Other Special Variables GNU make supports some variables that have special properties.13 Suppressing 64 GNU make. The other two directives that play a part in a conditional are else and endif.The if function provides support for conditional expansion in a functional context (as opposed to the GNU make makele conditionals such as ifeq (see Section 7.2 [Syntax of Conditionals], page 62). Any recursively invoked make command will still run recipes in parallel (unless its makefile also contains this target).(if condition,then-part [,else-part ]) The if function provides support for conditional expansion in a functional context (as opposed to the GNU make makefile conditionals GNU Make (short gmake) is the standard implementation of make for Linux and OS X.[11] It provides several extensions over the original make, such as conditionals.The GNU Make documentation refers to the commands associated with a rule as a " recipe". The GNU Make static pattern rules are understood. They are translated into recipe predicates.The GNU Make and BSD make conditionals are understood, provided that they bracket whole segments of the makefile, and that these segments are syntactically valid. This is done in a console using GNU Make. So, as part of the install, a console window pops open, you see the make file output wiz by as it compiles and links, when finished the console window closes and the installer continues. Conditionals can compare the value of one variable to another, or the value of a variable to a constant string. Conditionals control what make actually sees in the makefile, so they cannot be used to control recipes at the time of execution. (param) is expanded by GNU make.Variable and function references in recipes have identical syntax and semantics to references elsewhere in the makefile. I eventually found the solution in the GNU Make documentation.If you need to use automatic variables in a conditional directive you must move the condition into the recipe and use shell conditional syntax instead. gnu make file builds some code with the Keil compiler and creates a reg file within this context. The code should be recompiled until the reg file doesnt change any more.So at the time the ifneq is parsed none of the recipe has been invoked. If you want a conditional that runs as part of the recipe The following example of a conditional tells make to use one set of libraries if the CC variable is gcc, and a different set of libraries otherwise. It works by controlling which of two command lines will be used as the command for a rule. If you say make bar, make will find no way to make bar in GNUmakefile, so it will use the recipe from the pattern rule: make -f Makefile bar.The if function provides support for conditional expansion in a functional context (as opposed to the GNU make makefile conditionals such as ifeq (see Syntax of The following example of a conditional tells make to use one set of libraries if the CC variable is gcc, and a different set of libraries otherwise. It works by controlling which of two command lines will be used as the command for a rule. Macro: AMCONDITIONAL (conditional, condition). The conditional name, conditional, should be a simple string starting with a letter and containing only letters, digits, and underscores.Note that conditionals in Automake are not the same as conditionals in GNU Make. Make will complain about multiple recipes for the same rule.sport tennis Conditional compilation report: ifeq ((sport),tennis) echo game, set, match else echo "They think its all over it is now" endif .More Resources. gnu make documentation. software carpentry tutorial. More "gnu make conditional" pdf. Advertisement.cond n [expr] new conditional expression on breakpoint n make unconditional if no expr tbreak it under the terms of the GNU General Public License. make evaluates conditionals when it reads a makefile. Consequently, you cannot use automatic variables in the tests of conditionals because they are not defined until commands are run (see section Automatic Variables). 21/12/2017 GNU make: Conditional Syntax. Next: Testing may safely be split across the beginning or the end of the conditional. make evaluates conditionals when it Am I doing something wrong? Im using GNU Make v4.1 in Cygwin, I also confirmed this behavior in Linux with GNU Make v3.81.To pass down, or export, a variable, make adds the variable and its value to the environment for running each line of the recipe. But then why did it print false? Because before make parses the results of the evaluation, it first expands the string to be evaluated.

The info function is being expanded when the argument to eval is being expanded, before make parses the code. The GNU Make static pattern rules are understood. They are translated into recipe predicates.The GNU Make and BSD make conditionals are understood, provided that they bracket whole segments of the makefile, and that these segments are syntactically valid. In The Practice of Programming, Kernighan Pike recommend that you use the intersection of different systems features, not the union of features, to avoid conditionalIt allows you to write multi-line recipes without explicitly escaping newlines see Using One Shell in the GNU make manual. GNU make. For a quick summary, see Section 9.7 Options Summary, page 605, Appendix A Quick Reference, page 653, and Section 4.7 Special Tar-gets, page 543.make evaluates conditionals when it reads a makele. GNU Make provides a rich set of conditional directives, with which you can annotate parts of the Makefile to be used conditionally (or ignored). Make conditional directives work in very much the same way as C preprocessor directives (of the GCC chapter (FIXME Macro: AMCONDITIONAL (conditional, condition). The conditional name, conditional, should be a simple string starting with a letter and containing only letters, digits, and underscores.Note that conditionals in Automake are not the same as conditionals in GNU Make. In contrast, GNU Make expands variables in dependency lists at parse time (along with conditional syntax), but expands variables in recipe bodies later. This can cause differences between GNU and Biomake in situations where variables change value throughout the Makefile. I believe this is wrong because then i have to create a new shell to execute the conditional statement.How to list prerequisites externally in GNU Make? 1. Using environment variables for shorter recipes in GNU Make. 1. Undefined Variables in Conditionals.GNU make has no way of detecting that some targets ought to be rebuilt, because it doesnt take into account any change to the commands in recipes. I have looked at the Gnu Make manual in the "implicit rules" and "automatic variables" sections but I did not found a better way.This is how automake does this type of configuration. You could also use a make conditional around these lines This is Edition 0.72, last updated 9 October 2013, of The GNU Make Manual , for GNU make version 4.0.What happens after a recipe execution error. 5.6 Interrupting or Killing make.Example of a conditional. 7.2 Syntax of Conditionals. GNU Make provides a rich set of conditional directives, with which you can annotate parts of the Makefile to be used conditionally (or ignored). Make conditional directives work in very much the same way as C preprocessor directives (of the GCC chapter (FIXME Apparently there is no boolean type in GNU Make conditionals so this seemed like the best solutionWhy does it fail when X and Y are assigned values in the target recipe? Check the GNU make manual and youll see that make imports all environment variables as make variables.It doesnt matter if they appear inside recipes, or what. Values that are set via target-specific rules, on the other hand, are always parsed during the second phase. A conditional causes part of a makefile to be obeyed or ignored depending on the values of variables.Conditionals control what make actually sees in the makefile, so they cannot be used to control shell commands at the time of execution. Conditionals control what make actually "sees" in the makefile, so they cannot be used to control shell commands at the time of execution.Published under the terms of the GNU General Public License. Two different types of prerequisites understood by GNU make: Normal prerequisites: imposes an order in which recipes will be invoked, and imposes a dependency relationship.The main use of MAKELEVEL is to test it in a conditional directive this way you can write a makefile that behaves 5 Writing Recipes in Rules. 6 How to Use Variables. 7 Conditional Parts of Makefiles. 8 Functions for Transforming Text.14 Features of GNU make. 15 Incompatibilities and Missing Features. 16 Makefile Conventions. If you want to test something inside a recipe that was the result of running another recipe, you have to either use functions like (if) or else use shell if-statements, not make ifeq etc.

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