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resource:sc_lab_info:fedora:makefiles [2016/03/27 11:35] rim created |
resource:sc_lab_info:fedora:makefiles [2023/02/15 12:46] |
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| - | ====== Makefiles ====== | ||
| - | Makefiles are command files used by the "make" or "gmake" system to create a software system (or sometimes other object, such as documentation) from sources. | ||
| - | The important thing for //users// to remember is\\ | ||
| - | == Never Execute a Makefile == | ||
| - | The syntax is fairly different from shell or other scripts; nevertheless, it occurs surprisingly often that a shell interpreter is able to 'interpret' the first few lines of a makefile. If, as often occurs, the first template happens to be one for uninstalling the package, the results can be disastrous. For example, if the variables $dir, $base and $ext haven't been initialised in a way the shell can understand, then | ||
| - | rm $dir/$base*$ext | ||
| - | might well get interpreted as | ||
| - | rm /* | ||
| - | |||
| - | ====== ====== | ||
| - | |||
| - | The important thing for //developers// to remember is\\ | ||
| - | == Always protect Users from Executing a Makefile == | ||
| - | For the reasons above, I strongly recommend, if you are writing a makefile, to include as early as possible in your file something like: | ||
| - | |||
| - | # Template to protect users against accidentally | ||
| - | # executing a makefile - skipped if called by make | ||
| - | # if called as a script, | ||
| - | # it should barf on the unexpected "ifeq", | ||
| - | # but even if it manages to ignore that, | ||
| - | # it should print and exit | ||
| - | # Note that this protection is needed, because makefiles | ||
| - | # can sometimes be valid shell scripts - witness the | ||
| - | # standard XMILL makefile that manages to skip errors | ||
| - | # till it gets to | ||
| - | # clean: | ||
| - | # rm -r -f $(TMP)/* $(TARGETS) | ||
| - | # when executed in most unix shells - | ||
| - | # which isn't very nice if $(TMP) is undefined... | ||
| - | ifeq (1,0) | ||
| - | echo "THIS IS NOT A SHELL SCRIPT!!!!" | ||
| - | echo "IT IS A CONFIGURATION FILE FOR THE make SYSTEM" | ||
| - | echo "DO NOT EXECUTE IT" | ||
| - | exit 1 | ||
| - | endif | ||
| - | |||
| - | This won't affect the execution of the makefile at all, because 1 will never equal 0 (so the nested part will never even be seen by make) | ||
| - | |||
| - | It works as a protection in all unix shells I have tried; it may not work as well in DOS, but I assume it would at least cause an abort. | ||