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author | Jacob Kroon <jacob.kroon@gmail.com> | 2020-03-19 00:17:37 +0100 |
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committer | Richard Purdie <richard.purdie@linuxfoundation.org> | 2020-03-19 11:28:25 +0000 |
commit | 4780df48d5998d619dc36b699400e344187fc134 (patch) | |
tree | 370fd8858b35e2c7fb2a207a3924965ac9682fdf | |
parent | a37189fbdba399437cb9fcb28aa963515679cc65 (diff) | |
download | bitbake-4780df48d5998d619dc36b699400e344187fc134.tar.gz |
bitbake-user-manual: immediate-variable-expansion: Correct description
References to undefined variables are preserved as is and do not
expand to nothing as in GNU Make.
Signed-off-by: Jacob Kroon <jacob.kroon@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
-rw-r--r-- | doc/bitbake-user-manual/bitbake-user-manual-metadata.xml | 15 |
1 files changed, 9 insertions, 6 deletions
diff --git a/doc/bitbake-user-manual/bitbake-user-manual-metadata.xml b/doc/bitbake-user-manual/bitbake-user-manual-metadata.xml index bb5a7f861..10b588352 100644 --- a/doc/bitbake-user-manual/bitbake-user-manual-metadata.xml +++ b/doc/bitbake-user-manual/bitbake-user-manual-metadata.xml @@ -294,17 +294,20 @@ rather than when the variable is actually used: <literallayout class='monospaced'> T = "123" - A := "${B} ${A} test ${T}" + A := "test ${T}" T = "456" - B = "${T} bval" + B := "${T} ${C}" C = "cval" C := "${C}append" </literallayout> In this example, <filename>A</filename> contains - "test 123" because <filename>${B}</filename> and - <filename>${A}</filename> at the time of parsing are undefined, - which leaves "test 123". - And, the variable <filename>C</filename> + "test 123", even though the final value of <filename>T</filename> + is "456". + The variable <filename>B</filename> will end up containing "456 cvalappend". + This is because references to undefined variables are preserved as is + during (immediate)expansion. This is in contrast to GNU Make, where undefined + variables expand to nothing. + The variable <filename>C</filename> contains "cvalappend" since <filename>${C}</filename> immediately expands to "cval". </para> |