[PATCH 2/2] erofs-utils: support liblzma auto-detection

[Gao Xiang]

The new XZ Utils 5.4 is now available in most Linux distributions.

Let's enable liblzma auto-detection as well as get rid of MicroLZMA
EXPERIMENTAL warning.

Signed-off-by: Gao Xiang <hsiangkao at linux.alibaba.com>
---
 configure.ac             | 54 ++++++++++++++++++----------------------
 lib/compressor_liblzma.c |  3 +--
 2 files changed, 25 insertions(+), 32 deletions(-)

diff --git a/configure.ac b/configure.ac
index cd14beb..87c8492 100644
--- a/configure.ac
+++ b/configure.ac
@@ -119,8 +119,8 @@ AC_ARG_ENABLE(lz4,
    [enable_lz4="$enableval"], [enable_lz4="yes"])
 
 AC_ARG_ENABLE(lzma,
-   [AS_HELP_STRING([--enable-lzma], [enable LZMA compression support @<:@default=no@:>@])],
-   [enable_lzma="$enableval"], [enable_lzma="no"])
+   [AS_HELP_STRING([--disable-lzma], [disable LZMA compression support @<:@default=auto@:>@])],
+   [enable_lzma="$enableval"])
 
 AC_ARG_WITH(zlib,
    [AS_HELP_STRING([--without-zlib],
@@ -161,14 +161,6 @@ AC_ARG_WITH(lz4-libdir,
 AC_ARG_VAR([LZ4_CFLAGS], [C compiler flags for lz4])
 AC_ARG_VAR([LZ4_LIBS], [linker flags for lz4])
 
-AC_ARG_WITH(liblzma-incdir,
-   [AS_HELP_STRING([--with-liblzma-incdir=DIR], [liblzma include directory])], [
-   EROFS_UTILS_PARSE_DIRECTORY(["$withval"],[withval])])
-
-AC_ARG_WITH(liblzma-libdir,
-   [AS_HELP_STRING([--with-liblzma-libdir=DIR], [liblzma lib directory])], [
-   EROFS_UTILS_PARSE_DIRECTORY(["$withval"],[withval])])
-
 # Checks for header files.
 AC_CHECK_HEADERS(m4_flatten([
 	dirent.h
@@ -400,30 +392,32 @@ if test "x$enable_lz4" = "xyes"; then
   CPPFLAGS=${saved_CPPFLAGS}
 fi
 
-if test "x$enable_lzma" = "xyes"; then
+# Configure liblzma
+have_liblzma="no"
+AS_IF([test "x$enable_lzma" != "xno"], [
   saved_CPPFLAGS=${CPPFLAGS}
-  test -z "${with_liblzma_incdir}" ||
-    CPPFLAGS="-I$with_liblzma_incdir $CPPFLAGS"
-  AC_CHECK_HEADERS([lzma.h],[have_lzmah="yes"], [])
-
-  if test "x${have_lzmah}" = "xyes" ; then
+  PKG_CHECK_MODULES([liblzma], [liblzma], [
+    # Paranoia: don't trust the result reported by pkgconfig before trying out
     saved_LIBS="$LIBS"
-    saved_LDFLAGS="$LDFLAGS"
-
-    test -z "${with_liblzma_libdir}" ||
-      LDFLAGS="-L$with_liblzma_libdir ${LDFLAGS}"
-    AC_CHECK_LIB(lzma, lzma_microlzma_encoder, [],
-      [AC_MSG_ERROR([Cannot find proper liblzma])])
-
-    AC_CHECK_DECL(lzma_microlzma_encoder, [have_liblzma="yes"],
-      [AC_MSG_ERROR([Cannot find proper liblzma])], [[
+    saved_CPPFLAGS=${CPPFLAGS}
+    CPPFLAGS="${liblzma_CFLAGS} ${CPPFLAGS}"
+    LIBS="${liblzma_LIBS} $LIBS"
+    AC_CHECK_HEADERS([lzma.h],[
+      AC_CHECK_LIB(lzma, lzma_microlzma_encoder, [],
+        [AC_MSG_ERROR([Cannot find proper liblzma])])
+
+      AC_CHECK_DECL(lzma_microlzma_encoder, [have_liblzma="yes"],
+        [AC_MSG_ERROR([Cannot find proper liblzma])], [[
 #include <lzma.h>
-    ]])
-    LDFLAGS="${saved_LDFLAGS}"
+      ]])
+    ])
     LIBS="${saved_LIBS}"
-  fi
-  CPPFLAGS="${saved_CPPFLAGS}"
-fi
+    CPPFLAGS="${saved_CPPFLAGS}" ], [
+    AS_IF([test "x$enable_lzma" = "xyes"], [
+      AC_MSG_ERROR([Cannot find proper liblzma])
+    ])
+  ])
+])
 
 # Configure zlib
 have_zlib="no"
diff --git a/lib/compressor_liblzma.c b/lib/compressor_liblzma.c
index 7183b0b..712f44f 100644
--- a/lib/compressor_liblzma.c
+++ b/lib/compressor_liblzma.c
@@ -103,8 +103,7 @@ static int erofs_compressor_liblzma_init(struct erofs_compress *c)
 	ctx->opt.dict_size = c->dict_size;
 
 	c->private_data = ctx;
-	erofs_warn("EXPERIMENTAL MicroLZMA feature in use. Use at your own risk!");
-	erofs_warn("Note that it may take more time since the compressor is still single-threaded for now.");
+	erofs_warn("It may take a longer time since MicroLZMA is still single-threaded for now.");
 	return 0;
 }
 
-- 
2.39.3