avr-libc: add support for avr-libc C library

This commit adds support for the avr-libc C library.
According to the project page at http://www.nongnu.org/avr-libc , the
avr-libc package provides a subset of the standard C library for Atmel
AVR 8-bit RISC microcontrollers. In addition, the library provides the
basic startup code needed by most applications.

Support for this library in crosstool-ng is only enabled for the AVR
8-bit target.

The avr-libc manual and most distributions build the AVR 8-bit gcc
toolchain with the "avr" (non-canonical) target.
Some experimentation also led to the conclusion that other (canonical)
targets are not very well supported, so we force the "avr" target for
crosstool-ng as well.

The manual also recommends building avr-libc after the final gcc build.
To accomplish this with crosstool-ng, a new do_libc_post_cc step is
added, in which currently only avr-libc performs its build, and is a
no-op for the other libc options.

Signed-off-by: Erico Nunes <nunes.erico@gmail.com>

config/libc/avr-libc.in

@@ -0,0 +1,51 @@
+# avr-libc options
+
+## depends on ARCH_avr
+## depends on ! LINUX && ! WINDOWS && BARE_METAL
+##
+## select LIBC_SUPPORT_THREADS_NONE
+##
+## help The AVR Libc package provides a subset of the standard C library for
+## help Atmel AVR 8-bit RISC microcontrollers. In addition, the library
+## help provides the basic startup code needed by most applications.
+
+choice
+    bool
+    prompt "avr-libc version"
+# Don't remove next line
+# CT_INSERT_VERSION_BELOW
+
+config LIBC_AVR_LIBC_V_1_8_1
+    bool
+    prompt "1.8.1"
+
+config LIBC_AVR_LIBC_V_1_8_0
+    bool
+    prompt "1.8.0"
+
+config LIBC_AVR_LIBC_CUSTOM
+    bool
+    prompt "Custom avr-libc"
+    depends on EXPERIMENTAL
+
+endchoice
+
+if LIBC_AVR_LIBC_CUSTOM
+
+config LIBC_AVR_LIBC_CUSTOM_LOCATION
+    string
+    prompt "Full path to custom avr-libc source"
+    default ""
+    help
+      Enter the path to the directory (or tarball) of your source for avr-libc,
+      or leave blank to use default CT_CUSTOM_LOCATION_ROOT_DIR/avr-libc
+
+endif # LIBC_AVR_LIBC_CUSTOM
+
+config LIBC_VERSION
+    string
+# Don't remove next line
+# CT_INSERT_VERSION_STRING_BELOW
+    default "1.8.1" if LIBC_AVR_LIBC_V_1_8_1
+    default "1.8.0" if LIBC_AVR_LIBC_V_1_8_0
+    default "custom" if LIBC_AVR_LIBC_CUSTOM

config/libc/avr-libc.in.2

@@ -0,0 +1,8 @@
+# avr-libc second-part options
+
+config LIBC_AVR_LIBC_EXTRA_CONFIG_ARRAY
+    string
+    prompt "Extra config for avr-libc"
+    default ""
+    help
+      Extra flags to pass onto ./configure when configuring the avr-libc.

config/toolchain.in

@@ -99,6 +99,7 @@ comment "Tuple completion and aliasing"
 config TARGET_VENDOR
     string
     prompt "Tuple's vendor string"
+    depends on !LIBC_avr_libc
     default "unknown"
     help
       Vendor part of the target tuple.

scripts/build/libc/avr-libc.sh

@@ -0,0 +1,71 @@
+# This file adds functions to build the avr-libc C library
+
+do_libc_get() {
+    local libc_src
+
+    libc_src="http://download.savannah.gnu.org/releases/avr-libc"
+
+    if [ "${CT_LIBC_AVR_LIBC_CUSTOM}" = "y" ]; then
+        CT_GetCustom "avr-libc" "${CT_LIBC_VERSION}"      \
+                     "${CT_LIBC_AVR_LIBC_CUSTOM_LOCATION}"
+    else # ! custom location
+        CT_GetFile "avr-libc-${CT_LIBC_VERSION}" "${libc_src}"
+    fi # ! custom location
+}
+
+do_libc_extract() {
+    # If using custom directory location, nothing to do.
+    if [ "${CT_LIBC_AVR_LIBC_CUSTOM}" = "y" ]; then
+        # Abort if the custom directory is not found.
+        if ! [ -d "${CT_SRC_DIR}/avr-libc-${CT_LIBC_VERSION}" ]; then
+            CT_Abort "Directory not found: ${CT_SRC_DIR}/avr-libc-${CT_LIBC_VERSION}"
+        fi
+
+        return 0
+    fi
+
+    CT_Extract "avr-libc-${CT_LIBC_VERSION}"
+    CT_Patch "avr-libc" "${CT_LIBC_VERSION}"
+}
+
+do_libc_check_config() {
+    :
+}
+
+do_libc_configure() {
+    CT_DoLog EXTRA "Configuring C library"
+
+    CT_DoExecLog CFG                \
+    ./configure                     \
+        --build=${CT_BUILD}         \
+        --host=${CT_TARGET}         \
+        --prefix=${CT_PREFIX_DIR}   \
+        "${CT_LIBC_AVR_LIBC_EXTRA_CONFIG_ARRAY[@]}"
+}
+
+do_libc_start_files() {
+    :
+}
+
+do_libc() {
+    :
+}
+
+do_libc_post_cc() {
+    CT_DoStep INFO "Installing C library"
+
+    CT_DoLog EXTRA "Copying sources to build directory"
+    CT_DoExecLog ALL cp -av "${CT_SRC_DIR}/avr-libc-${CT_LIBC_VERSION}" \
+                            "${CT_BUILD_DIR}/build-libc-post-cc"
+    cd "${CT_BUILD_DIR}/build-libc-post-cc"
+
+    do_libc_configure
+
+    CT_DoLog EXTRA "Building C library"
+    CT_DoExecLog ALL make ${JOBSFLAGS}
+
+    CT_DoLog EXTRA "Installing C library"
+    CT_DoExecLog ALL make install
+
+    CT_EndStep
+}

scripts/build/libc/glibc.sh

@@ -665,3 +665,7 @@ do_libc_locales() {
                           install_root="${CT_SYSROOT_DIR}"          \
                           localedata/install-locales
 }
+
+do_libc_post_cc() {
+    :
+}

scripts/build/libc/mingw.sh

@@ -112,3 +112,7 @@ do_libc() {
 
     CT_EndStep
 }
+
+do_libc_post_cc() {
+    :
+}

scripts/build/libc/musl.sh

@@ -113,3 +113,7 @@ do_libc() {
 
     CT_EndStep
 }
+
+do_libc_post_cc() {
+    :
+}

scripts/build/libc/newlib.sh

@@ -149,3 +149,7 @@ do_libc() {
 
     CT_EndStep
 }
+
+do_libc_post_cc() {
+    :
+}

scripts/build/libc/none.sh

@@ -21,3 +21,7 @@ do_libc_start_files() {
 do_libc() {
     :
 }
+
+do_libc_post_cc() {
+    :
+}

scripts/build/libc/uClibc.sh

@@ -554,3 +554,7 @@ mungeuClibcConfig() {
 
     sed -r -f "${munge_file}" "${src_config_file}" >"${dst_config_file}"
 }
+
+do_libc_post_cc() {
+    :
+}

scripts/functions

@@ -1206,6 +1206,11 @@ CT_DoBuildTargetTuple() {
         *glibc) CT_TARGET_SYS=gnu;;
         uClibc) CT_TARGET_SYS=uclibc;;
         musl)   CT_TARGET_SYS=musl;;
+        avr-libc)
+            # avr-libc only seems to work with the non-canonical "avr" target.
+            CT_TARGET_SKIP_CONFIG_SUB=y
+            CT_TARGET_SYS= # CT_TARGET_SYS must be empty too
+        ;;
         *)      CT_TARGET_SYS=elf;;
     esac
 
@@ -1259,7 +1264,10 @@ CT_DoBuildTargetTuple() {
     esac
 
     # Canonicalise it
+    if [ "${CT_TARGET_SKIP_CONFIG_SUB}" != "y" ]; then
         CT_TARGET=$(CT_DoConfigSub "${CT_TARGET}")
+    fi
+
     # Prepare the target CFLAGS
     CT_ARCH_TARGET_CFLAGS="${CT_ARCH_TARGET_CFLAGS} ${CT_ARCH_ENDIAN_CFLAG}"
     CT_ARCH_TARGET_CFLAGS="${CT_ARCH_TARGET_CFLAGS} ${CT_ARCH_ARCH_CFLAG}"

steps.mk

@@ -30,6 +30,7 @@ CT_STEPS := libc_check_config        \
             libc                     \
             cc_for_build             \
             cc_for_host              \
+            libc_post_cc             \
             libelf_for_target        \
             binutils_for_target      \
             debug                    \