From: Michal Privoznik <[email protected]>
In shell, the following function doesn't echo '1' but '0':
func() {
local var=$(false)
echo $?
}
This is because '$?' does not refer to 'false' but 'local'. The
bash_builtins(1) manpage explains it well. And it also mentions
other commands behaving the same: export, declare and readonly.
Since it is really easy to miss this pattern, introduce a
syntax-check rule. Mind you, the following patter (which passes
the rule) does check for the subshell exit code:
func() {
local var
var=$(false)
echo $?
}
Signed-off-by: Michal Privoznik <[email protected]>
---
build-aux/syntax-check.mk | 11 +++++++++++
1 file changed, 11 insertions(+)
diff --git a/build-aux/syntax-check.mk b/build-aux/syntax-check.mk
index f605c9b0e3..022e8e6550 100644
--- a/build-aux/syntax-check.mk
+++ b/build-aux/syntax-check.mk
@@ -394,6 +394,17 @@ sc_prohibit_g_autofree_const:
halt='‘g_autofree’ discards ‘const’ qualifier from pointer target type'
\
$(_sc_search_regexp)
+sc_prohibit_local_with_subshell:
+ @err=0; for f in $$($(VC_LIST_EXCEPT) | $(GREP) -E '\.sh(\.in)?$$'); do
\
+ lines=$$( $(AWK) \
+ '/^\s*(local|export|declare|readonly)\s+.*=/ { nr=NR; c=1; next } \
+ /^\s*$$/ { if (c) next } \
+ /\$$\?/ { if (c) { print nr; c=0; } next } \
+ { c=0 }' $$f ) ; \
+ for l in $$lines; do echo $$f:$$l 1>&2; err=1; done ; \
+ done; \
+ test $$err -eq 0 || { msg="Declare and assign separately to avoid
masking return values" $(_sc_say_and_exit) }
+
# Many of the function names below came from this filter:
# git grep -B2 '\<_('|grep -E '\.c- *[[:alpha:]_][[:alnum:]_]* ?\(.*[,;]$' \
--
2.52.0
