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11.2 Failure in Make Rules
Since 1992 Posix has required that make must invoke
each command with the equivalent of a ‘sh -c’ subshell. However,
many make implementations, including BSD make through 2004,
use ‘sh -e -c’ instead, and the -e option causes the
subshell to exit immediately if a subsidiary simple-command fails. For
example, the command ‘touch T; rm -f U’ always attempts to
remove U with Posix make, but incompatible
make implementations skip the rm if the
touch fails. One way to work around this is to reword the
affected simple-commands so that they always succeed, e.g., ‘touch
T || :; rm -f U’.
However, even this approach can run into common bugs in BSD
implementations of the -e option of sh and
set (see Limitations of Builtins), so if you are worried
about porting to buggy BSD shells it may be simpler to migrate
complicated make actions into separate scripts.
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