Go patch committed: Move reading export data to gcc interface

[Ian Lance Taylor <iant at google dot com>]

This patch moves reading export data from an object file out of the Go
frontend proper into the gcc side of the interface.  The purpose of this
move is to let the gcc side entirely control the name of the Mach-O
segment and section where the export data is stored.  Bootstrapped and
ran Go testsuite on x86_64-unknown-linux-gnu.  Committed to mainline.

Ian


2011-12-13  Ian Lance Taylor  <iant@google.com>

	* go-backend.c: #include "simple-object.h" and "intl.h".
	(GO_EXPORT_SEGMENT_NAME): Define if not defined.
	(GO_EXPORT_SECTION_NAME): Likewise.
	(go_write_export_data): Use GO_EXPORT_SECTION_NAME.
	(go_read_export_data): New function.
	* go-c.h (go_read_export_data): Declare.


Index: gcc/go/gofrontend/import.h
===================================================================
--- gcc/go/gofrontend/import.h	(revision 181813)
+++ gcc/go/gofrontend/import.h	(working copy)
@@ -287,7 +287,7 @@ class Stream_from_string : public Import
   size_t pos_;
 };
 
-// Read import data from an allocated buffer.
+// Read import data from a buffer allocated using malloc.
 
 class Stream_from_buffer : public Import::Stream
 {
@@ -297,7 +297,7 @@ class Stream_from_buffer : public Import
   { }
 
   ~Stream_from_buffer()
-  { delete[] this->buf_; }
+  { free(this->buf_); }
 
  protected:
   bool
Index: gcc/go/gofrontend/import.cc
===================================================================
--- gcc/go/gofrontend/import.cc	(revision 181889)
+++ gcc/go/gofrontend/import.cc	(working copy)
@@ -215,46 +215,24 @@ Import::find_object_export_data(const st
 				off_t offset,
 				Location location)
 {
-  const char* errmsg;
+  char *buf;
+  size_t len;
   int err;
-  simple_object_read* sobj = simple_object_start_read(fd, offset,
-						      "__GNU_GO",
-						      &errmsg, &err);
-  if (sobj == NULL)
-    return NULL;
-
-  off_t sec_offset;
-  off_t sec_length;
-  int found = simple_object_find_section(sobj, ".go_export", &sec_offset,
-					 &sec_length, &errmsg, &err);
-
-  simple_object_release_read(sobj);
-
-  if (!found)
-    return NULL;
-
-  if (lseek(fd, offset + sec_offset, SEEK_SET) < 0)
+  const char *errmsg = go_read_export_data(fd, offset, &buf, &len, &err);
+  if (errmsg != NULL)
     {
-      error_at(location, "lseek %s failed: %m", filename.c_str());
+      if (err == 0)
+	error_at(location, "%s: %s", filename.c_str(), errmsg);
+      else
+	error_at(location, "%s: %s: %s", filename.c_str(), errmsg,
+		 xstrerror(err));
       return NULL;
     }
 
-  char* buf = new char[sec_length];
-  ssize_t c = read(fd, buf, sec_length);
-  if (c < 0)
-    {
-      error_at(location, "read %s failed: %m", filename.c_str());
-      delete[] buf;
-      return NULL;
-    }
-  if (c < sec_length)
-    {
-      error_at(location, "%s: short read", filename.c_str());
-      delete[] buf;
-      return NULL;
-    }
+  if (buf == NULL)
+    return NULL;
 
-  return new Stream_from_buffer(buf, sec_length);
+  return new Stream_from_buffer(buf, len);
 }
 
 // Class Import.
Index: gcc/go/go-c.h
===================================================================
--- gcc/go/go-c.h	(revision 181628)
+++ gcc/go/go-c.h	(working copy)
@@ -69,6 +69,8 @@ extern void go_imported_unsafe (void);
 
 extern void go_write_export_data (const char *, unsigned int);
 
+extern const char *go_read_export_data (int, off_t, char **, size_t *, int *);
+
 #if defined(__cplusplus) && !defined(ENABLE_BUILD_WITH_CXX)
 } /* End extern "C".  */
 #endif
Index: gcc/go/go-backend.c
===================================================================
--- gcc/go/go-backend.c	(revision 181628)
+++ gcc/go/go-backend.c	(working copy)
@@ -20,16 +20,31 @@ along with GCC; see the file COPYING3.  
 #include "config.h"
 #include "system.h"
 #include "coretypes.h"
+#include "simple-object.h"
 #include "tm.h"
 #include "rtl.h"
 #include "tree.h"
 #include "tm_p.h"
+#include "intl.h"
 #include "output.h"
 #include "target.h"
 #include "common/common-target.h"
 
 #include "go-c.h"
 
+/* The segment name we pass to simple_object_start_read to find Go
+   export data.  */
+
+#ifndef GO_EXPORT_SEGMENT_NAME
+#define GO_EXPORT_SEGMENT_NAME "__GNU_GO"
+#endif
+
+/* The section name we use when reading and writing export data.  */
+
+#ifndef GO_EXPORT_SECTION_NAME
+#define GO_EXPORT_SECTION_NAME ".go_export"
+#endif
+
 /* This file holds all the cases where the Go frontend needs
    information from gcc's backend.  */
 
@@ -95,7 +110,7 @@ go_imported_unsafe (void)
 }
 
 /* This is called by the Go frontend proper to add data to the
-   .go_export section.  */
+   section containing Go export data.  */
 
 void
 go_write_export_data (const char *bytes, unsigned int size)
@@ -105,9 +120,87 @@ go_write_export_data (const char *bytes,
   if (sec == NULL)
     {
       gcc_assert (targetm_common.have_named_sections);
-      sec = get_section (".go_export", SECTION_DEBUG, NULL);
+      sec = get_section (GO_EXPORT_SECTION_NAME, SECTION_DEBUG, NULL);
     }
 
   switch_to_section (sec);
   assemble_string (bytes, size);
 }
+
+/* The go_read_export_data function is called by the Go frontend
+   proper to read Go export data from an object file.  FD is a file
+   descriptor open for reading.  OFFSET is the offset within the file
+   where the object file starts; this will be 0 except when reading an
+   archive.  On success this returns NULL and sets *PBUF to a buffer
+   allocated using malloc, of size *PLEN, holding the export data.  If
+   the data is not found, this returns NULL and sets *PBUF to NULL and
+   *PLEN to 0.  If some error occurs, this returns an error message
+   and sets *PERR to an errno value or 0 if there is no relevant
+   errno.  */
+
+const char *
+go_read_export_data (int fd, off_t offset, char **pbuf, size_t *plen,
+		     int *perr)
+{
+  simple_object_read *sobj;
+  const char *errmsg;
+  off_t sec_offset;
+  off_t sec_length;
+  int found;
+  char *buf;
+  ssize_t c;
+
+  *pbuf = NULL;
+  *plen = 0;
+
+  sobj = simple_object_start_read (fd, offset, GO_EXPORT_SEGMENT_NAME,
+				   &errmsg, perr);
+  if (sobj == NULL)
+    {
+      /* If we get an error here, just pretend that we didn't find any
+	 export data.  This is the right thing to do if the error is
+	 that the file was not recognized as an object file.  This
+	 will ignore file I/O errors, but it's not too big a deal
+	 because we will wind up giving some other error later.  */
+      return NULL;
+    }
+
+  found = simple_object_find_section (sobj, GO_EXPORT_SECTION_NAME,
+				      &sec_offset, &sec_length,
+				      &errmsg, perr);
+  simple_object_release_read (sobj);
+  if (!found)
+    return errmsg;
+
+  if (lseek (fd, offset + sec_offset, SEEK_SET) < 0)
+    {
+      *perr = errno;
+      return _("lseek failed while reading export data");
+    }
+
+  buf = XNEWVEC (char, sec_length);
+  if (buf == NULL)
+    {
+      *perr = errno;
+      return _("memory allocation failed while reading export data");
+    }
+
+  c = read (fd, buf, sec_length);
+  if (c < 0)
+    {
+      *perr = errno;
+      free (buf);
+      return _("read failed while reading export data");
+    }
+
+  if (c < sec_length)
+    {
+      free (buf);
+      return _("short read while reading export data");
+    }
+
+  *pbuf = buf;
+  *plen = sec_length;
+
+  return NULL;
+}