[3.6] closes bpo-22140: Prevent double substitution of prefix in python-config.sh (GH-3769) (#3793)

Fix the logic in python-config.sh to avoid attempting to substitute prefix in a variable that might have already been subject to substitution. This e.g. happened if @exec_prefix@ was defined as "${prefix}" (which is the default of the configure script) -- in which case the exec_prefix_build variable was initialized with already-subtituted prefix, and then another round of substitution was performed which might have resulted in duplicate prefix. To avoid that, rename the variables so that the variables matching likely configure names (prefix, exec_prefix) retain their original values and a '_real' suffix is used for the real values of prefix. Furthermore, replace the unnecessary prefix and exec_prefix substitutions with direct prefix_real references since the sed always replaced the whole string anyway by design. (cherry picked from commit 14086cf)

Author: benjaminp

Misc/NEWS.d/next/Build/2017-09-26-22-39-58.bpo-22140.ZRf7Wn.rst

@@ -0,0 +1 @@
+Prevent double substitution of prefix in python-config.sh.

Misc/python-config.sh.in

@@ -24,17 +24,18 @@ installed_prefix ()
  echo $RESULT
 }
 
-prefix_build="@prefix@"
 prefix_real=$(installed_prefix "$0")
 
 # Use sed to fix paths from their built-to locations to their installed-to
-# locations.
-prefix=$(echo "$prefix_build" | sed "s#$prefix_build#$prefix_real#")
-exec_prefix_build="@exec_prefix@"
-exec_prefix=$(echo "$exec_prefix_build" | sed "s#$exec_prefix_build#$prefix_real#")
-includedir=$(echo "@includedir@" | sed "s#$prefix_build#$prefix_real#")
-libdir=$(echo "@libdir@" | sed "s#$prefix_build#$prefix_real#")
-CFLAGS=$(echo "@CFLAGS@" | sed "s#$prefix_build#$prefix_real#")
+# locations. Keep prefix & exec_prefix using their original values in case
+# they are referenced in other configure variables, to prevent double
+# substitution, issue #22140.
+prefix="@prefix@"
+exec_prefix="@exec_prefix@"
+exec_prefix_real=${prefix_real}
+includedir=$(echo "@includedir@" | sed "s#$prefix#$prefix_real#")
+libdir=$(echo "@libdir@" | sed "s#$prefix#$prefix_real#")
+CFLAGS=$(echo "@CFLAGS@" | sed "s#$prefix#$prefix_real#")
 VERSION="@VERSION@"
 LIBM="@LIBM@"
 LIBC="@LIBC@"
@@ -47,8 +48,8 @@ LINKFORSHARED="@LINKFORSHARED@"
 OPT="@OPT@"
 PY_ENABLE_SHARED="@PY_ENABLE_SHARED@"
 LDVERSION="@LDVERSION@"
-LIBDEST=${prefix}/lib/python${VERSION}
-LIBPL=$(echo "@LIBPL@" | sed "s#$prefix_build#$prefix_real#")
+LIBDEST=${prefix_real}/lib/python${VERSION}
+LIBPL=$(echo "@LIBPL@" | sed "s#$prefix#$prefix_real#")
 SO="@EXT_SUFFIX@"
 PYTHONFRAMEWORK="@PYTHONFRAMEWORK@"
 INCDIR="-I$includedir/python${VERSION}${ABIFLAGS}"
@@ -73,10 +74,10 @@ for ARG in "$@"
 do
  case "$ARG" in
  --prefix)
- echo "$prefix"
+ echo "$prefix_real"
  ;;
  --exec-prefix)
- echo "$exec_prefix"
+ echo "$exec_prefix_real"
  ;;
  --includes)
  echo "$INCDIR $PLATINCDIR"