Use multilib concept with Clang/ATfE

cmake/preload/toolchains/pico_arm_cortex_m0plus_clang.cmake

@@ -1,7 +1,7 @@
 set(CMAKE_SYSTEM_PROCESSOR cortex-m0plus)
 
 # these are all the directories under LLVM embedded toolchain for ARM (newlib or pibolibc) and under llvm_libc
-set(PICO_CLANG_RUNTIMES armv6m_soft_nofp armv6m-unknown-none-eabi)
+set(PICO_CLANG_RUNTIMES armv6m_soft_nofp armv6m_soft_nofp_size armv6m-unknown-none-eabi)
 
 set(PICO_COMMON_LANG_FLAGS "--target=armv6m-none-eabi -mfloat-abi=soft -march=armv6m")
 

cmake/preload/toolchains/pico_arm_cortex_m33_clang.cmake

@@ -1,7 +1,7 @@
 set(CMAKE_SYSTEM_PROCESSOR cortex-m33)
 
 # these are all the directories under LLVM embedded toolchain for ARM (newlib or pibolibc) and under llvm_libc
-set(PICO_CLANG_RUNTIMES armv8m.main_soft_nofp armv8m.main_soft_nofp_unaligned armv8m.main-unknown-none-eabi)
+set(PICO_CLANG_RUNTIMES armv8m.main_soft_nofp armv8m.main_soft_nofp_unaligned armv8m.main_soft_nofp_unaligned_size armv8m.main-unknown-none-eabi)
 
 set(PICO_COMMON_LANG_FLAGS "-mcpu=cortex-m33 --target=armv8m.main-none-eabi -mfloat-abi=softfp -march=armv8m.main+fp+dsp")
 set(PICO_DISASM_OBJDUMP_ARGS --mcpu=cortex-m33 --arch=armv8m.main+fp+dsp)

cmake/preload/toolchains/util/pico_arm_clang_common.cmake

@@ -43,12 +43,30 @@ endforeach()
 
 list(APPEND CMAKE_TRY_COMPILE_PLATFORM_VARIABLES PICO_CLIB)
 
+set(_PICO_CLIB_PATH "${PICO_COMPILER_DIR}/../lib/clang-runtimes/arm-none-eabi")
+if(PICO_CLIB STREQUAL ""  OR  PICO_CLIB STREQUAL "newlib")
+    # newlib is 1st class choice
+    if(EXISTS "${PICO_COMPILER_DIR}/../lib/clang-runtimes/newlib/arm-none-eabi")
+        set(_PICO_CLIB_PATH "${PICO_COMPILER_DIR}/../lib/clang-runtimes/newlib/arm-none-eabi")
+    endif()
+elseif(PICO_CLIB STREQUAL "llvm_libc")
+    if(EXISTS "${PICO_COMPILER_DIR}/../lib/clang-runtimes/llvmlibc/arm-none-eabi")
+        set(_PICO_CLIB_PATH "${PICO_COMPILER_DIR}/../lib/clang-runtimes/llvmlibc/arm-none-eabi")
+    endif()
+elseif(PICO_CLIB STREQUAL "picolibc")
+    if(EXISTS "${PICO_COMPILER_DIR}/../lib/clang-runtimes/picolibc/arm-none-eabi")
+        set(_PICO_CLIB_PATH "${PICO_COMPILER_DIR}/../lib/clang-runtimes/picolibc/arm-none-eabi")
+    endif()
+else()
+    message(FATAL_ERROR "PICO_CLIB must be one of newlib, picolib, llvm_libc or empty (but is '${PICO_CLIB}')")
+endif()
+
 foreach(PICO_CLANG_RUNTIME IN LISTS PICO_CLANG_RUNTIMES)
     # LLVM embedded-toolchain for ARM style
-    find_path(PICO_COMPILER_SYSROOT NAMES include/stdio.h
+    find_path(PICO_COMPILER_SYSROOT NAMES lib/libc.a
             HINTS
-            ${PICO_COMPILER_DIR}/../lib/clang-runtimes/arm-none-eabi/${PICO_CLANG_RUNTIME}
-            ${PICO_COMPILER_DIR}/../lib/clang-runtimes/${PICO_CLANG_RUNTIME}
+                ${_PICO_CLIB_PATH}/${PICO_CLANG_RUNTIME}
+                ${PICO_COMPILER_DIR}/../lib/clang-runtimes/${PICO_CLANG_RUNTIME}
     )
 
     if (PICO_COMPILER_SYSROOT)
@@ -66,7 +84,7 @@ foreach(PICO_CLANG_RUNTIME IN LISTS PICO_CLANG_RUNTIMES)
     # llvm_libc style
     find_path(PICO_COMPILER_SYSROOT NAMES stdio.h
             HINTS
-            ${PICO_COMPILER_DIR}/../include/${PICO_CLANG_RUNTIME}
+                ${PICO_COMPILER_DIR}/../include/${PICO_CLANG_RUNTIME}
     )
     if (PICO_COMPILER_SYSROOT)
         if (NOT PICO_CLIB)
@@ -76,6 +94,19 @@ foreach(PICO_CLANG_RUNTIME IN LISTS PICO_CLANG_RUNTIMES)
         break()
     endif()
 endforeach()
+if (NOT PICO_COMPILER_SYSROOT)
+    message(FATAL_ERROR "Could not find an llvm runtime for '${PICO_CLANG_RUNTIME}'")
+endif()
+set(PICO_COMMON_LANG_FLAGS "${PICO_COMMON_LANG_FLAGS} --sysroot ${PICO_COMPILER_SYSROOT}")
+
+# add some system includes due to structure of ATfE-21.1.1 header structure
+# required for llvmlibc / newlib, NOT for picolibc
+if(EXISTS "${PICO_COMPILER_SYSROOT}/../include/c++/v1")
+    set(PICO_COMMON_LANG_FLAGS "${PICO_COMMON_LANG_FLAGS} -isystem ${PICO_COMPILER_SYSROOT}/../include/c++/v1")
+endif()
+if(EXISTS "${PICO_COMPILER_SYSROOT}/../include")
+    set(PICO_COMMON_LANG_FLAGS "${PICO_COMMON_LANG_FLAGS} -isystem ${PICO_COMPILER_SYSROOT}/../include")
+endif()
 
 # moving this here as a reminder from pico_standard_link; it was commented out theee, but if ever needed,
 # it belongs here as part of LINKER_FLAGS_INIT
@@ -87,11 +118,5 @@ if (PICO_CLIB STREQUAL "llvm_libc")
     foreach(TYPE IN ITEMS EXE SHARED MODULE)
         set(CMAKE_${TYPE}_LINKER_FLAGS_INIT "-nostdlib++ -nostartfiles")
     endforeach()
-else()
-    if (NOT PICO_COMPILER_SYSROOT)
-        message(FATAL_ERROR "Could not find an llvm runtime for '${PICO_CLANG_RUNTIME}'")
-    endif()
-
-    set(PICO_COMMON_LANG_FLAGS "${PICO_COMMON_LANG_FLAGS} --sysroot ${PICO_COMPILER_SYSROOT}")
 endif()
 include(${CMAKE_CURRENT_LIST_DIR}/set_flags.cmake)

src/rp2_common/pico_clib_interface/BUILD.bazel

@@ -98,10 +98,16 @@ cc_library(
     target_compatible_with = compatible_with_rp2(),
 )
 
-# For now, picolibc doesn't need to provide any headers.
-alias(
+cc_library(
     name = "picolibc_interface",
-    actual = "//bazel:empty_cc_lib",
+    hdrs = [
+        "include/picolibc/sys/cdefs.h",
+    ],
+    includes = ["include/picolibc"],
+    # It's hard to properly constrain compatibility since `auto` may select this,
+    # so just tag as manual.
+    tags = ["manual"],
+    target_compatible_with = compatible_with_rp2(),
 )
 
 cc_library(

src/rp2_common/pico_clib_interface/CMakeLists.txt

@@ -21,6 +21,10 @@ if (NOT TARGET pico_clib_interface)
     #            PICO_STDIO_SHORT_CIRCUIT_CLIB_FUNCS=0
     #)
 
+    target_include_directories(pico_picolibc_interface SYSTEM INTERFACE
+            ${CMAKE_CURRENT_LIST_DIR}/include/picolibc
+    )
+
     #  ---- llvm_libc ----
     pico_add_library(pico_llvm_libc_interface)
 

src/rp2_common/pico_clib_interface/include/llvm_libc/time.h

@@ -9,15 +9,15 @@
 
 #include <__llvm-libc-common.h>
 
+#include <llvm-libc-types/struct_timespec.h>
 #include <llvm-libc-types/struct_tm.h>
 #include <llvm-libc-types/time_t.h>
 
 __BEGIN_C_DECLS
 
 struct tm* localtime_r(const time_t* timer, struct tm* buf);
+time_t mktime(struct tm *);
 
 __END_C_DECLS
 
-#include_next <time.h>
-
 #endif // _PICO_LLVM_LIBC_TIME_H

src/rp2_common/pico_clib_interface/include/picolibc/sys/cdefs.h

@@ -0,0 +1,32 @@
+/*
+ * Copyright (c) 2020 Raspberry Pi (Trading) Ltd.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#ifndef __PICO_PICOLIBC_SYS_CDEFS_H
+#define __PICO_PICOLIBC_SYS_CDEFS_H
+
+#if defined(__STDC__) || defined(__cplusplus)
+
+#define __CONCAT1(x,y)  x ## y
+#define __CONCAT(x,y)   __CONCAT1(x,y)
+#define __STRING(x)     #x
+#define __XSTRING(x)    __STRING(x)
+
+#endif
+
+#define __unused        __attribute__((__unused__))
+#define __used          __attribute__((__used__))
+#define __packed        __attribute__((__packed__))
+#define __aligned(x)    __attribute__((__aligned__(x)))
+
+#define __always_inline __inline__ __attribute__((__always_inline__))
+#define __noinline      __attribute__((__noinline__))
+
+#define __printflike(fmtarg, firstvararg) \
+  __attribute__((__format__ (__printf__, fmtarg, firstvararg)))
+
+#include_next <sys/cdefs.h>
+
+#endif

src/rp2_common/pico_clib_interface/llvm_libc_interface.c

@@ -7,11 +7,11 @@
 #include <math.h>
 #include <stdbool.h>
 #include <stddef.h>
-#include <sys/time.h>
-#include <time.h>
-
 #include <llvm-libc-types/ssize_t.h>
 
+#include "include/llvm_libc/time.h"
+#include "include/llvm_libc/sys/time.h"
+
 #include "pico/runtime_init.h"
 #include "pico/stdio.h"
 #include "pico/time.h"