cgo: add stdio support to picolibc

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 +12,17 @@ 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",
+			"-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 +31,105 @@ 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",

lib/picolibc-stdio.c

@@ -0,0 +1,12 @@
+#include <stdio.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 __iob[3] = { &__stdio, &__stdio, &__stdio };

src/runtime/baremetal.go

@@ -51,6 +51,11 @@ func libc_abort() {
 	abort()
 }
 
+//export runtime_putchar
+func runtime_putchar(c byte) {
+	putchar(c)
+}
+
 //go:linkname syscall_Exit syscall.Exit
 func syscall_Exit(code int) {
 	abort()

testdata/cgo/main.go

@@ -139,6 +139,8 @@ func main() {
 
 	// libc: test basic stdio functionality
 	println("SEEK_CUR:", C.SEEK_CUR)
+	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 @@ enum width matches: true
 CFLAGS value: 17
 copied string: foobar
 SEEK_CUR: 1
+line written using C puts