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On the cygwin list, a difference was pointed out between compilations of
bash that avoid or use --with-installed-readline:
static_bash$ echo $HOME ~
/home/eblake /home/eblake
static_bash$ HOME=/tmp; echo $HOME ~
/tmp /tmp
dynamic_bash$ echo $HOME ~
/home/eblake /home/eblake
dynamic_bash$ HOME=/tmp; echo $HOME ~
/tmp /home/eblake
When compiling statically (without using --with-installed-readline), bash
uses its own -ltilde, and sh_get_env_value resolves to bash's
implementation in variable.c, which correctly searches bash's alternative
environment.
When compiling dynamically out of the box (using
- --with-installed-readline), there is a link error of multiply defined
symbols. The problem here is that bash wants to use the static -ltilde
but the dynamic libreadline.dll; but since cygwin forbids dynamic
libraries with undefined symbols, libreadline.dll was already compiled
with -ltilde and all the symbols from -ltilde conflict with those from the
dynamic library. My patch to this issue is below.
When compiling dynamically with the patch applied, bash gets its
tilde-expansion routines from the dynamic libreadline. Unfortunately,
when compiling libreadline, sh_get_env_value resolves to readline's
version in shell.c, which just calls getenv(). Cygwin does not allow
bash's sh_get_env_value (or getenv) to override libreadline.dll's version
(back to that no undefined symbol rule - tilde.c cannot link into a
dynamic library with an import of sh_get_env_value unless sh_get_env_value
is defined as part of the dynamic library). So tilde expansion is now
stuck reading the global environ instead of bash's environment, and since
bash does not update environ, tilde expansion is frozen to the value of
$HOME at process invocation.
I think the best solution would be a backwards-compatible extension to the
tilde library. It should provide a new exported variable that defaults to
NULL (in which case tilde_expand_word falls back to calling the imported
sh_get_env_value), but which applications can set to override the calls to
sh_get_env_value (and thus sh_get_home_dir). It could either be a char*
(the current string representing HOME/home_dir in bash's notion of the
environment) or a function pointer (a callback that lets bash compute the
current HOME or home_dir every time it is needed), I'm not sure which of
those two options would be easier for bash. This new export would bump
the API version of readline (to 5.1?), and then compiling bash
- --with-installed-readline would have to use this new entry point so that
it can tell tilde_expand_word what to use so that tilde-expansion isn't
stuck expanding from a stale environment.
- --- bash-3.0-orig/configure.in 2004-07-21 14:06:54.000000000 -0600
+++ bash-3.0/configure.in 2005-05-24 20:29:34.000000000 -0600
@@ -487,14 +487,15 @@
esac
;;
esac
- - READLINE_DEP=
+ READLINE_DEP= TILDE_LIB=
else
RL_LIBDIR='$(dot)/$(LIBSUBDIR)/readline'
READLINE_DEP='$(READLINE_LIBRARY)'
+ TILDE_LIB=-ltilde
fi
else
RL_LIBDIR='$(dot)/$(LIBSUBDIR)/readline'
- - READLINE_LIB= READLINE_DEP=
+ READLINE_LIB= READLINE_DEP= TILDE_LIB=-ltilde
fi
if test $opt_history = yes || test $opt_bang_history = yes; then
if test $opt_history = yes; then
@@ -528,6 +529,7 @@
AC_SUBST(RL_LIBDIR)
AC_SUBST(RL_INCLUDEDIR)
AC_SUBST(RL_INCLUDE)
+AC_SUBST(TILDE_LIB)
AC_SUBST(HISTORY_LIB)
AC_SUBST(HISTORY_DEP)
AC_SUBST(HIST_LIBDIR)
- --- bash-3.0-orig/Makefile.in 2004-03-17 06:34:39.000000000 -0700
+++ bash-3.0/Makefile.in 2005-07-06 05:59:58.000000000 -0600
@@ -309,7 +309,7 @@
TILDE_LIBDIR = $(dot)/$(LIBSUBDIR)/tilde
TILDE_ABSSRC = ${topdir}/$(TILDE_LIBDIR)
- -TILDE_LIB = -ltilde
+TILDE_LIB = @TILDE_LIB@
TILDE_LIBRARY = $(TILDE_LIBDIR)/libtilde.a
TILDE_LDFLAGS = -L$(TILDE_LIBDIR)
TILDE_DEP = $(TILDE_LIBRARY)
- --
Life is short - so eat dessert first!
Eric Blake [EMAIL PROTECTED]
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