cgo: add support for stdio in picolibc and wasi-libc

This adds support for stdio in picolibc and fixes wasm_exec.js so that
it can also support C puts. With this, C stdout works on all supported
platforms.

Dockerfile

@@ -15,7 +15,7 @@ RUN cd /tinygo/ && \
     git submodule sync && \
     git submodule update --init --recursive --force
 
-COPY ./lib/picolibc-include/* /tinygo/lib/picolibc-include/
+COPY ./lib/picolibc-* /tinygo/lib/
 
 RUN cd /tinygo/ && \
     go install /tinygo/

Makefile

@@ -480,6 +480,7 @@ build/release: tinygo gen-device wasi-libc
 	@mkdir -p build/release/tinygo/lib/compiler-rt/lib
 	@mkdir -p build/release/tinygo/lib/nrfx
 	@mkdir -p build/release/tinygo/lib/picolibc/newlib/libc
+	@mkdir -p build/release/tinygo/lib/picolibc/newlib/libm
 	@mkdir -p build/release/tinygo/lib/wasi-libc
 	@mkdir -p build/release/tinygo/pkg/armv6m-unknown-unknown-eabi
 	@mkdir -p build/release/tinygo/pkg/armv7m-unknown-unknown-eabi
@@ -498,7 +499,9 @@ build/release: tinygo gen-device wasi-libc
 	@cp -rp lib/picolibc/newlib/libc/locale      build/release/tinygo/lib/picolibc/newlib/libc
 	@cp -rp lib/picolibc/newlib/libc/string      build/release/tinygo/lib/picolibc/newlib/libc
 	@cp -rp lib/picolibc/newlib/libc/tinystdio   build/release/tinygo/lib/picolibc/newlib/libc
+	@cp -rp lib/picolibc/newlib/libm/common      build/release/tinygo/lib/picolibc/newlib/libm
 	@cp -rp lib/picolibc-include         build/release/tinygo/lib
+	@cp -rp lib/picolibc-stdio.c         build/release/tinygo/lib
 	@cp -rp lib/wasi-libc/sysroot        build/release/tinygo/lib/wasi-libc/sysroot
 	@cp -rp src                          build/release/tinygo/src
 	@cp -rp targets                      build/release/tinygo/targets

builder/ar.go

@@ -5,6 +5,7 @@ import (
 	"debug/elf"
 	"encoding/binary"
 	"errors"
+	"fmt"
 	"io"
 	"os"
 	"path/filepath"
@@ -49,7 +50,7 @@ func makeArchive(archivePath string, objs []string) error {
 		// Read the symbols and add them to the symbol table.
 		dbg, err := elf.NewFile(objfile)
 		if err != nil {
-			return err
+			return fmt.Errorf("failed to open file %s: %w", objpath, err)
 		}
 		symbols, err := dbg.Symbols()
 		if err != nil {
@@ -61,9 +62,8 @@ func makeArchive(archivePath string, objs []string) error {
 				// Don't include local symbols (STB_LOCAL).
 				continue
 			}
-			if elf.ST_TYPE(symbol.Info) != elf.STT_FUNC {
+			if elf.ST_TYPE(symbol.Info) != elf.STT_FUNC && elf.ST_TYPE(symbol.Info) != elf.STT_OBJECT {
 				// Not a function.
-				// TODO: perhaps globals variables should also be included?
 				continue
 			}
 			// Include in archive.

builder/picolibc.go

@@ -12,7 +12,18 @@ var Picolibc = Library{
 	name: "picolibc",
 	cflags: func() []string {
 		picolibcDir := filepath.Join(goenv.Get("TINYGOROOT"), "lib/picolibc/newlib/libc")
-		return []string{"-Werror", "-Wall", "-std=gnu11", "-D_COMPILING_NEWLIB", "-nostdlibinc", "-Xclang", "-internal-isystem", "-Xclang", picolibcDir + "/include", "-I" + picolibcDir + "/tinystdio", "-I" + goenv.Get("TINYGOROOT") + "/lib/picolibc-include"}
+		return []string{
+			"-Werror",
+			"-Wall",
+			"-std=gnu11",
+			"-D_COMPILING_NEWLIB",
+			"-DHAVE_ALIAS_ATTRIBUTE",
+			"-DTINY_STDIO",
+			"-nostdlibinc",
+			"-Xclang", "-internal-isystem", "-Xclang", picolibcDir + "/include",
+			"-I" + picolibcDir + "/tinystdio",
+			"-I" + goenv.Get("TINYGOROOT") + "/lib/picolibc-include",
+		}
 	},
 	sourceDir: "lib/picolibc/newlib/libc",
 	sources: func(target string) []string {
@@ -21,6 +32,105 @@ var Picolibc = Library{
 }
 
 var picolibcSources = []string{
+	"../../../picolibc-stdio.c",
+
+	"tinystdio/asprintf.c",
+	"tinystdio/atod_engine.c",
+	"tinystdio/atod_ryu.c",
+	"tinystdio/atof_engine.c",
+	"tinystdio/atof_ryu.c",
+	//"tinystdio/atold_engine.c", // have_long_double and not long_double_equals_double
+	"tinystdio/clearerr.c",
+	"tinystdio/compare_exchange.c",
+	"tinystdio/dtoa_data.c",
+	"tinystdio/dtoa_engine.c",
+	"tinystdio/dtoa_ryu.c",
+	"tinystdio/ecvtbuf.c",
+	"tinystdio/ecvt.c",
+	"tinystdio/ecvt_data.c",
+	"tinystdio/ecvtfbuf.c",
+	"tinystdio/ecvtf.c",
+	"tinystdio/ecvtf_data.c",
+	"tinystdio/exchange.c",
+	//"tinystdio/fclose.c", // posix-io
+	"tinystdio/fcvtbuf.c",
+	"tinystdio/fcvt.c",
+	"tinystdio/fcvtfbuf.c",
+	"tinystdio/fcvtf.c",
+	"tinystdio/fdevopen.c",
+	//"tinystdio/fdopen.c", // posix-io
+	"tinystdio/feof.c",
+	"tinystdio/ferror.c",
+	"tinystdio/fflush.c",
+	"tinystdio/fgetc.c",
+	"tinystdio/fgets.c",
+	"tinystdio/fileno.c",
+	"tinystdio/filestrget.c",
+	"tinystdio/filestrputalloc.c",
+	"tinystdio/filestrput.c",
+	//"tinystdio/fopen.c", // posix-io
+	"tinystdio/fprintf.c",
+	"tinystdio/fputc.c",
+	"tinystdio/fputs.c",
+	"tinystdio/fread.c",
+	"tinystdio/fscanf.c",
+	"tinystdio/fseek.c",
+	"tinystdio/ftell.c",
+	"tinystdio/ftoa_data.c",
+	"tinystdio/ftoa_engine.c",
+	"tinystdio/ftoa_ryu.c",
+	"tinystdio/fwrite.c",
+	"tinystdio/gcvtbuf.c",
+	"tinystdio/gcvt.c",
+	"tinystdio/gcvtfbuf.c",
+	"tinystdio/gcvtf.c",
+	"tinystdio/getchar.c",
+	"tinystdio/gets.c",
+	"tinystdio/matchcaseprefix.c",
+	"tinystdio/perror.c",
+	//"tinystdio/posixiob.c", // posix-io
+	//"tinystdio/posixio.c", // posix-io
+	"tinystdio/printf.c",
+	"tinystdio/putchar.c",
+	"tinystdio/puts.c",
+	"tinystdio/ryu_divpow2.c",
+	"tinystdio/ryu_log10.c",
+	"tinystdio/ryu_log2pow5.c",
+	"tinystdio/ryu_pow5bits.c",
+	"tinystdio/ryu_table.c",
+	"tinystdio/ryu_umul128.c",
+	"tinystdio/scanf.c",
+	"tinystdio/setbuf.c",
+	"tinystdio/setvbuf.c",
+	//"tinystdio/sflags.c", // posix-io
+	"tinystdio/snprintf.c",
+	"tinystdio/snprintfd.c",
+	"tinystdio/snprintff.c",
+	"tinystdio/sprintf.c",
+	"tinystdio/sprintfd.c",
+	"tinystdio/sprintff.c",
+	"tinystdio/sscanf.c",
+	"tinystdio/strfromd.c",
+	"tinystdio/strfromf.c",
+	"tinystdio/strtod.c",
+	"tinystdio/strtod_l.c",
+	"tinystdio/strtof.c",
+	//"tinystdio/strtold.c",   // have_long_double and not long_double_equals_double
+	//"tinystdio/strtold_l.c", // have_long_double and not long_double_equals_double
+	"tinystdio/ungetc.c",
+	"tinystdio/vasprintf.c",
+	"tinystdio/vfiprintf.c",
+	"tinystdio/vfiscanf.c",
+	"tinystdio/vfprintf.c",
+	"tinystdio/vfprintff.c",
+	"tinystdio/vfscanf.c",
+	"tinystdio/vfscanff.c",
+	"tinystdio/vprintf.c",
+	"tinystdio/vscanf.c",
+	"tinystdio/vsnprintf.c",
+	"tinystdio/vsprintf.c",
+	"tinystdio/vsscanf.c",
+
 	"string/bcmp.c",
 	"string/bcopy.c",
 	"string/bzero.c",

compileopts/config.go

@@ -206,7 +206,12 @@ func (c *Config) CFlags() []string {
 	}
 	if c.Target.Libc == "picolibc" {
 		root := goenv.Get("TINYGOROOT")
-		cflags = append(cflags, "-nostdlibinc", "-Xclang", "-internal-isystem", "-Xclang", filepath.Join(root, "lib", "picolibc", "newlib", "libc", "include"))
+		picolibcDir := filepath.Join(root, "lib", "picolibc", "newlib", "libc")
+		cflags = append(cflags,
+			"-nostdlibinc",
+			"-Xclang", "-internal-isystem", "-Xclang", filepath.Join(picolibcDir, "include"),
+			"-Xclang", "-internal-isystem", "-Xclang", filepath.Join(picolibcDir, "tinystdio"),
+		)
 		cflags = append(cflags, "-I"+filepath.Join(root, "lib/picolibc-include"))
 	}
 	// Always emit debug information. It is optionally stripped at link time.

lib/picolibc-stdio.c

@@ -0,0 +1,18 @@
+// This file is included in the picolibc build.
+// It makes stdio functions available to the C library.
+
+#include <stdio.h>
+#include <sys/cdefs.h>
+
+// Defined in the runtime package. Writes to the default console (usually, the
+// first UART or an USB-CDC device).
+int runtime_putchar(char, FILE*);
+
+// Define stdin, stdout, and stderr as a single object.
+// This object must not reside in ROM.
+static FILE __stdio = FDEV_SETUP_STREAM(runtime_putchar, NULL, NULL, _FDEV_SETUP_WRITE);
+
+// Define the underlying structs for stdin, stdout, and stderr.
+FILE *const stdin = &__stdio;
+__strong_reference(stdin, stdout);
+__strong_reference(stdin, stderr);

src/runtime/baremetal.go

@@ -46,6 +46,11 @@ func libc_free(ptr unsafe.Pointer) {
 	free(ptr)
 }
 
+//export runtime_putchar
+func runtime_putchar(c byte) {
+	putchar(c)
+}
+
 //go:linkname syscall_Exit syscall.Exit
 func syscall_Exit(code int) {
 	exit(code)

targets/wasm_exec.js

@@ -256,6 +256,7 @@
 								let iov_ptr = iovs_ptr+iovs_i*8; // assuming wasm32
 								let ptr = mem().getUint32(iov_ptr + 0, true);
 								let len = mem().getUint32(iov_ptr + 4, true);
+								nwritten += len;
 								for (let i=0; i<len; i++) {
 									let c = mem().getUint8(ptr+i);
 									if (c == 13) { // CR
@@ -276,6 +277,9 @@
 						mem().setUint32(nwritten_ptr, nwritten, true);
 						return 0;
 					},
+					fd_close: () => 0,      // dummy
+					fd_fdstat_get: () => 0, // dummy
+					fd_seek: () => 0,       // dummy
 					"proc_exit": (code) => {
 						if (global.process) {
 							// Node.js

testdata/cgo/main.go

@@ -1,6 +1,7 @@
 package main
 
 /*
+#include <stdio.h>
 int fortytwo(void);
 #include "main.h"
 int mul(int, int);
@@ -139,6 +140,10 @@ func main() {
 	buf2 := make([]byte, len(buf1))
 	C.strcpy((*C.char)(unsafe.Pointer(&buf2[0])), (*C.char)(unsafe.Pointer(&buf1[0])))
 	println("copied string:", string(buf2[:C.strlen((*C.char)(unsafe.Pointer(&buf2[0])))]))
+
+	// libc: test basic stdio functionality
+	putsBuf := []byte("line written using C puts\x00")
+	C.puts((*C.char)(unsafe.Pointer(&putsBuf[0])))
 }
 
 func printUnion(union C.joined_t) C.joined_t {

testdata/cgo/out.txt

@@ -62,3 +62,4 @@ option 3A: 21
 enum width matches: true
 CFLAGS value: 17
 copied string: foobar
+line written using C puts