Bug #18504: configure prints a warning when cross-compiling

• Status: Closed
• Assignee: shyouhei (Shyouhei Urabe)
• Target version: -
• Backport: 2.6: UNKNOWN, 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN

[mame (Yusuke Endoh)]

$ sudo apt-get install gcc-aarch64-linux-gnu
$ ./configure --host=aarch64-linux-gnu
downloading config.guess ... done
downloading config.sub ... done
checking build system type... x86_64-pc-linux-gnu
checking host system type... aarch64-unknown-linux-gnu
checking target system type... aarch64-unknown-linux-gnu
checking for aarch64-linux-gnu-gcc... aarch64-linux-gnu-gcc
checking for aarch64-linux-gnu-aarch64-linux-gnu-ld... no
checking for aarch64-linux-gnu-ld... aarch64-linux-gnu-ld
configure: WARNING: using cross tools not prefixed with host triplet

It attempts to find aarch64-linux-gnu-aarch64-linux-gnu-ld, which fails. Then it finds aarch64-linux-gnu-ld, but also it prints "WARNING: using cross tools not prefixed with host triplet".

I guess this was triggered by 2c96e04868477eaa1420945d57bf5b3adb521e84. @shyouhei (Shyouhei Urabe) Could you take a look?

[shyouhei (Shyouhei Urabe)]

I know what is going on. About the only thing we can do is to settle for that warning. It works nonetheless.

The problem is our --with-gcc= configure option. That way you can instruct which compiler to use. Then we have to find the right linker that understands proper link-time optimisation scheme that the user-input compiler employs.

In case of cross compilation autoconf also sets $CC. But from our point of view there is no way to tell if that aarch64-linux-gnu-gcc value was user-input or auto-genrated. We have to do the same thing (find the linker that comes with the compiler), which eventually succeeds, with a warning.

In order to suppress the warning we have to detect where the $CC value came from; which is impractical. Please just live with the annoyance, or give up --with-gcc.

[nobu (Nobuyoshi Nakada)]

What about this?

diff --git a/configure.ac b/configure.ac
index 4feefb57915..01e87c0a9b4 100644
--- a/configure.ac
+++ b/configure.ac
@@ -129,9 +129,9 @@ AC_ARG_WITH(gcc,
 	AS_HELP_STRING([--without-gcc], [never use gcc]),
 	[
 	AS_CASE([$withval],
-	    [no],  [: ${CC=cc}],
-	    [yes], [: ${CC=gcc}],
-	           [CC=$withval])])
+	    [no],  [with_gcc=cc],
+	    [yes], [with_gcc=gcc],
+	           [])])
 dnl If the user switches compilers, we can't believe the cache
 AS_IF([test ! -z "$ac_cv_prog_CC" -a ! -z "$CC" -a "$CC" != "$ac_cv_prog_CC"], [
   AC_MSG_ERROR(cached CC is different -- throw away $cache_file
@@ -143,16 +143,16 @@ RUBY_WASM_TOOLS
 AS_CASE(["${build_os}"],
 [linux*|cygwin*|msys*], [
     # Naruse prefers GCC on Linux
-    AC_CHECK_TOOLS([CC], [gcc clang cc])
+    AC_CHECK_TOOLS([CC], [${with_gcc} gcc clang cc])
 ],
 [solaris*], [
     # Clang on Solaris is largely untested.
     # https://bugs.ruby-lang.org/issues/17949
-    AC_CHECK_TOOLS([CC], [cc gcc])
+    AC_CHECK_TOOLS([CC], [${with_gcc} cc gcc])
 ], [
     # OpenBSD wants to prefer cc over gcc.
     # See https://github.com/ruby/ruby/pull/2443
-    AC_CHECK_TOOLS([CC], [cl.exe clang cc gcc c99 /usr/ucb/cc])
+    AC_CHECK_TOOLS([CC], [${with_gcc} cl.exe clang cc gcc c99 /usr/ucb/cc])
 ])
 
 AC_ARG_VAR([AR],       [Archiver command])

[nobu (Nobuyoshi Nakada)]

• Status changed from Assigned to Closed

Applied in changeset git|4113862c0068a8a95d752f5fdf14980f92cd41d7.

---

Do not search for commands with double tool prefixes [Bug #18504]

The CC found by AC_CHECK_TOOL is prefixed by the host triplet
when cross compiling. To search for commands with AC_CHECK_TOOL
based on that CC means to search also doubly prefixed names.