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