Add libfmt to bypass output buffering for libmisc:assert

11 files changed, 137 insertions, 15 deletions

diff --git a/CMakeLists.txt b/CMakeLists.txt
index f9e2d72..22756c1 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -119,6 +119,7 @@ endfunction()
 
 add_subdirectory(libmisc)
 add_subdirectory(libobj)
+add_subdirectory(libfmt)
 add_subdirectory(libcr)
 add_subdirectory(libcr_ipc)
 add_subdirectory(libhw_generic)
diff --git a/build-aux/measurestack/app_main.py b/build-aux/measurestack/app_main.py
index 397dc31..9a31338 100644
--- a/build-aux/measurestack/app_main.py
+++ b/build-aux/measurestack/app_main.py
@@ -49,6 +49,7 @@ def main(
     plugins += [
         app_plugins.CmdPlugin(),
         libobj_plugin,
+        app_plugins.PicoFmtPlugin(arg_pico_platform),
         app_plugins.LibHWPlugin(arg_pico_platform, libobj_plugin),
         app_plugins.LibCRPlugin(),
         app_plugins.LibCRIPCPlugin(),
@@ -67,7 +68,6 @@ def main(
             return ret
 
         plugins += [
-            app_plugins.PicoFmtPlugin(),
             app_plugins.PicoSDKPlugin(
                 get_init_array=get_init_array,
             ),
@@ -88,10 +88,12 @@ def main(
         return 0, False
 
     def misc_filter(name: QName) -> tuple[int, bool]:
-        if name.base() in [
-            BaseName("__assert_msg_fail"),
-            BaseName("fmt_vfctprintf"),
-            BaseName("fmt_vsnprintf"),
+        if name in [
+            QName("__assert_msg_fail"),
+            QName("__lm_printf"),
+            QName("__lm_light_printf"),
+            QName("fmt_vfctprintf"),
+            QName("fmt_vsnprintf"),
         ]:
             return 1, False
         return 0, False
diff --git a/build-aux/measurestack/app_plugins.py b/build-aux/measurestack/app_plugins.py
index 1eee739..064ea06 100644
--- a/build-aux/measurestack/app_plugins.py
+++ b/build-aux/measurestack/app_plugins.py
@@ -448,7 +448,7 @@ class LibMiscPlugin:
     def _skipmodel___assert_msg_fail(
         self, chain: typing.Sequence[QName], call: QName
     ) -> bool:
-        if call.base() in [BaseName("__lm_printf")]:
+        if call.base() in [BaseName("__lm_printf"), BaseName("__lm_light_printf")]:
             return any(
                 c.base() == BaseName("__assert_msg_fail") for c in reversed(chain[:-1])
             )
@@ -458,14 +458,30 @@ class LibMiscPlugin:
 class PicoFmtPlugin:
     known_fct: dict[BaseName, BaseName]
 
-    def __init__(self) -> None:
+    def __init__(self, arg_pico_platform: str) -> None:
         self.known_fct = {
             # pico_fmt
             BaseName("fmt_vsnprintf"): BaseName("_out_buffer"),
-            # pico_stdio
-            BaseName("__wrap_vprintf"): BaseName("stdio_buffered_printer"),
-            BaseName("stdio_vprintf"): BaseName("stdio_buffered_printer"),
         }
+        match arg_pico_platform:
+            case "rp2040":
+                self.known_fct.update(
+                    {
+                        # pico_stdio
+                        BaseName("__wrap_vprintf"): BaseName("stdio_buffered_printer"),
+                        BaseName("stdio_vprintf"): BaseName("stdio_buffered_printer"),
+                        # libfmt
+                        BaseName("__lm_light_printf"): BaseName("libfmt_light_fct"),
+                    }
+                )
+            case "host":
+                self.known_fct.update(
+                    {
+                        # libfmt
+                        BaseName("__lm_printf"): BaseName("libfmt_libc_fct"),
+                        BaseName("__lm_light_printf"): BaseName("libfmt_libc_fct"),
+                    }
+                )
 
     def is_intrhandler(self, name: QName) -> bool:
         return False
diff --git a/cmd/sbc_harness/CMakeLists.txt b/cmd/sbc_harness/CMakeLists.txt
index fa42b47..64bf356 100644
--- a/cmd/sbc_harness/CMakeLists.txt
+++ b/cmd/sbc_harness/CMakeLists.txt
@@ -22,6 +22,7 @@ target_link_libraries(sbc_harness_objs
 	hardware_flash
 
 	libmisc
+	libfmt
 	libusb
 	libdhcp
 	libhw_cr
diff --git a/libfmt/CMakeLists.txt b/libfmt/CMakeLists.txt
new file mode 100644
index 0000000..b8db764
--- /dev/null
+++ b/libfmt/CMakeLists.txt
@@ -0,0 +1,14 @@
+# libfmt/CMakeLists.txt - Support for pico-fmt
+#
+# Copyright (C) 2025  Luke T. Shumaker <lukeshu@lukeshu.com>
+# SPDX-License-Identifier: AGPL-3.0-or-later
+
+add_library(libfmt INTERFACE)
+target_include_directories(libfmt SYSTEM INTERFACE ${CMAKE_CURRENT_SOURCE_DIR}/include)
+target_sources(libfmt INTERFACE
+	libmisc.c
+)
+target_link_libraries(libfmt INTERFACE
+	pico_fmt
+	libmisc
+)
diff --git a/libfmt/include/libfmt/fmt.h b/libfmt/include/libfmt/fmt.h
new file mode 100644
index 0000000..3f2d4e7
--- /dev/null
+++ b/libfmt/include/libfmt/fmt.h
@@ -0,0 +1,13 @@
+/* libfmt/fmt.h - Support for pico-fmt
+ *
+ * Copyright (C) 2025  Luke T. Shumaker <lukeshu@lukeshu.com>
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+#ifndef _LIBFMT_FMT_H_
+#define _LIBFMT_FMT_H_
+
+#include <pico/fmt_printf.h>
+#include <pico/fmt_install.h>
+
+#endif /* _LIBFMT_FMT_H_ */
diff --git a/libfmt/libmisc.c b/libfmt/libmisc.c
new file mode 100644
index 0000000..4586c30
--- /dev/null
+++ b/libfmt/libmisc.c
@@ -0,0 +1,59 @@
+/* libfmt/libmisc.c - Integrate pico-fmt with libmisc
+ *
+ * Copyright (C) 2024-2025  Luke T. Shumaker <lukeshu@lukeshu.com>
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+#include <stdarg.h>             /* for va_list, va_start(), va_end() */
+#include <stdio.h>              /* for vprintf(), putchar() */
+#if LIB_PICO_STDIO
+#include <pico/stdio.h>         /* for stdio_putchar_raw() */
+#endif
+
+#include <libmisc/macro.h>      /* for LM_UNUSED() */
+#include <libmisc/_intercept.h> /* for __lm_printf() and __lm_light_printf() */
+
+#include <libfmt/fmt.h>         /* for fmt_vfctprintf() */
+
+#if LIB_PICO_STDIO
+static void libfmt_light_fct(char character, void *LM_UNUSED(arg)) {
+	stdio_putchar_raw(character);
+}
+#else
+static void libfmt_libc_fct(char character, void *LM_UNUSED(arg)) {
+	putchar(character);
+}
+#endif
+
+int __lm_printf(const char *format, ...) {
+	va_list va;
+	va_start(va, format);
+#if LIB_PICO_STDIO
+	/* pico_stdio has already intercepted vprintf for us, and
+	 * their stdio_buffered_printer() is better than our
+	 * libfmt_libc_fct() because buffering.  */
+	int ret = vprintf(format, va);
+#else
+	int ret = fmt_vfctprintf(libfmt_libc_fct, NULL, format, va);
+#endif
+	va_end(va);
+	return ret;
+}
+
+int __lm_light_printf(const char *format, ...) {
+	va_list va;
+	va_start(va, format);
+#if LIB_PICO_STDIO
+	/* libfmt_light_fct() and stdio_buffered_printer() both use 68
+	 * bytes of stack; but the buffer lives on the stack of
+	 * stdio.c:__wrap_vprintf(); so that's where you'll see the
+	 * numbers be different if you're analyzing it.  (Also, being
+	 * able to skip the stdio_stack_buffer_flush() call.)  */
+	int ret = fmt_vfctprintf(libfmt_light_fct, NULL, format, va);
+	stdio_flush();
+#else
+	int ret = fmt_vfctprintf(libfmt_libc_fct, NULL, format, va);
+#endif
+	va_end(va);
+	return ret;
+}
diff --git a/libmisc/assert.c b/libmisc/assert.c
index 69c0530..fdd8154 100644
--- a/libmisc/assert.c
+++ b/libmisc/assert.c
@@ -1,6 +1,6 @@
 /* libmisc/assert.c - More assertions
  *
- * Copyright (C) 2024  Luke T. Shumaker <lukeshu@lukeshu.com>
+ * Copyright (C) 2024-2025  Luke T. Shumaker <lukeshu@lukeshu.com>
  * SPDX-License-Identifier: AGPL-3.0-or-later
  */
 
@@ -12,6 +12,7 @@
 #include <libmisc/assert.h>
 
 #ifndef NDEBUG
+#define __lm_printf __lm_light_printf
 void __assert_msg_fail(const char *expr,
                   const char *file, unsigned int line, const char *func,
                   const char *msg) {
diff --git a/libmisc/include/libmisc/_intercept.h b/libmisc/include/libmisc/_intercept.h
index 47e4620..ab76857 100644
--- a/libmisc/include/libmisc/_intercept.h
+++ b/libmisc/include/libmisc/_intercept.h
@@ -1,6 +1,6 @@
 /* libmisc/_intercept.h - Interceptable ("weak") functions
  *
- * Copyright (C) 2024  Luke T. Shumaker <lukeshu@lukeshu.com>
+ * Copyright (C) 2024-2025  Luke T. Shumaker <lukeshu@lukeshu.com>
  * SPDX-License-Identifier: AGPL-3.0-or-later
  */
 
@@ -18,4 +18,10 @@ int __lm_printf(const char *format, ...);
 
 [[noreturn]] void __lm_abort(void);
 
+/* __lm_light_printf is expected to have less stack use than regular
+ * __lm_printf, if possible.  */
+
+[[format(printf, 1, 2)]]
+int __lm_light_printf(const char *format, ...);
+
 #endif /* _LIBMISC__INTERCEPT_H_ */
diff --git a/libmisc/intercept.c b/libmisc/intercept.c
index dda8c09..85a3801 100644
--- a/libmisc/intercept.c
+++ b/libmisc/intercept.c
@@ -1,6 +1,6 @@
 /* libmisc/intercept.c - Interceptable ("weak") functions
  *
- * Copyright (C) 2024  Luke T. Shumaker <lukeshu@lukeshu.com>
+ * Copyright (C) 2024-2025  Luke T. Shumaker <lukeshu@lukeshu.com>
  * SPDX-License-Identifier: AGPL-3.0-or-later
  */
 
@@ -20,6 +20,15 @@ int __lm_printf(const char *format, ...) {
 }
 
 [[gnu::weak]]
+int __lm_light_printf(const char *format, ...) {
+	va_list va;
+	va_start(va, format);
+	int ret = vprintf(format, va);
+	va_end(va);
+	return ret;
+}
+
+[[gnu::weak]]
 void __lm_abort(void) {
 	abort();
 }
diff --git a/libmisc/tests/test_assert.c b/libmisc/tests/test_assert.c
index 3c2d6b6..15f9446 100644
--- a/libmisc/tests/test_assert.c
+++ b/libmisc/tests/test_assert.c
@@ -1,6 +1,6 @@
 /* libmisc/tests/test_assert.c - Tests for <libmisc/assert.h>
  *
- * Copyright (C) 2024  Luke T. Shumaker <lukeshu@lukeshu.com>
+ * Copyright (C) 2024-2025  Luke T. Shumaker <lukeshu@lukeshu.com>
  * SPDX-License-Identifier: AGPL-3.0-or-later
  */
 
@@ -35,7 +35,7 @@ void __lm_abort(void) {
 	longjmp(global_env, 1);
 }
 
-int __lm_printf(const char *format, ...) {
+int __lm_light_printf(const char *format, ...) {
 	va_list va;
 	va_start(va, format);
 	int ret = vasprintf(&global_log, format, va);