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Resolve some documentation issues

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* doc/make.texi (Interrupts): [SV 46193] Recommend defensive recipes
* doc/make.texi: [SV 49262] Clarify interaction of prerequisites and
non-terminal match-anything rules.
This commit is contained in:
Paul Smith 2020-01-16 15:14:53 -05:00
parent 3b5e47b2e2
commit dd6adfa454
1 changed files with 24 additions and 5 deletions
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doc/make.texi
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@ -4533,6 +4533,19 @@ target is updated in some atomic fashion, or exists only to record a
modification-time (its contents do not matter), or must exist at all
times to prevent other sorts of trouble.
Although @code{make} does its best to clean up there are certain situations
in which cleanup is impossible. For example, @code{make} may be killed by
an uncatchable signal. Or, one of the programs make invokes may be killed
or crash, leaving behind an up-to-date but corrupt target file: @code{make}
will not realize that this failure requires the target to be cleaned. Or
@code{make} itself may encounter a bug and crash.
For these reasons it's best to write @emph{defensive recipes}, which won't
leave behind corrupted targets even if they fail. Most commonly these
recipes create temporary files rather than updating the target directly,
then rename the temporary file to the final target name. Some compilers
already behave this way, so that you don't need to write a defensive recipe.
@node Recursion, Canned Recipes, Interrupts, Recipes
@section Recursive Use of @code{make}
@cindex recursion
@ -9918,6 +9931,10 @@ and linking with a single @code{cc} command. The optimized rule is used in
preference to the step-by-step chain because it comes earlier in the
ordering of rules.
Finally, for performance reasons @code{make} will not consider non-terminal
match-anything rules (i.e., @samp{%:}) when searching for a rule to
build a prerequisite of an implicit rule (@pxref{Match-Anything Rules}).
@node Pattern Rules, Last Resort, Chained Rules, Implicit Rules
@section Defining and Redefining Pattern Rules
@ -10407,9 +10424,10 @@ remade from any other files; therefore, @code{make} can save time by not
looking for ways to remake them.@refill
If you do not mark the match-anything rule as terminal, then it is
non-terminal. A non-terminal match-anything rule cannot apply to a file name
that indicates a specific type of data. A file name indicates a specific
type of data if some non-match-anything implicit rule target matches it.
non-terminal. A non-terminal match-anything rule cannot apply to a
prerequisite of an implicit rule, or to a file name that indicates a
specific type of data. A file name indicates a specific type of data
if some non-match-anything implicit rule target matches it.
For example, the file name @file{foo.c} matches the target for the pattern
rule @samp{%.c : %.y} (the rule to run Yacc). Regardless of whether this
@ -10646,8 +10664,9 @@ Make a list of all the pattern rules one of whose targets matches
matched against @var{t}; otherwise, against @var{n}.
@item
If any rule in that list is @emph{not} a match-anything rule, then
remove all non-terminal match-anything rules from the list.
If any rule in that list is @emph{not} a match-anything rule, or if
@var{t} is a prerequisite of an implicit rule, then remove all
non-terminal match-anything rules from the list.
@item
Remove from the list all rules with no recipe.