[PATCH v2 1/7] Introduce read_entire_file

[Tom Tromey <tom@tromey.com>]

This adds a new function, read_entire_file, and changes the source
cache to use it.  This will be used in a subsequent patch as well.

gdb/ChangeLog
2020-06-22  Tom Tromey  <tom@tromey.com>

	* utils.h (myread): Don't declare.
	* utils.c (myread): Remove.
	* source-cache.c (source_cache::get_plain_source_lines): Use
	read_entire_file.

gdbsupport/ChangeLog
2020-06-22  Tom Tromey  <tom@tromey.com>

	* filestuff.h (read_entire_file): Declare.
	* filestuff.cc (read_entire_file): New function.
---
 gdb/ChangeLog           |  7 +++++++
 gdb/source-cache.c      | 14 +++++---------
 gdb/utils.c             | 22 ----------------------
 gdb/utils.h             |  2 --
 gdbsupport/ChangeLog    |  5 +++++
 gdbsupport/filestuff.cc | 33 +++++++++++++++++++++++++++++++++
 gdbsupport/filestuff.h  |  9 +++++++++
 7 files changed, 59 insertions(+), 33 deletions(-)

diff --git a/gdb/source-cache.c b/gdb/source-cache.c
index 9196e3a19e3..63e08c3aeb0 100644
--- a/gdb/source-cache.c
+++ b/gdb/source-cache.c
@@ -18,6 +18,7 @@
 
 #include "defs.h"
 #include "source-cache.h"
+#include "gdbsupport/filestuff.h"
 #include "gdbsupport/scoped_fd.h"
 #include "source.h"
 #include "cli/cli-style.h"
@@ -56,14 +57,9 @@ source_cache::get_plain_source_lines (struct symtab *s,
   if (desc.get () < 0)
     perror_with_name (symtab_to_filename_for_display (s));
 
-  struct stat st;
-  if (fstat (desc.get (), &st) < 0)
-    perror_with_name (symtab_to_filename_for_display (s));
-
-  std::string lines;
-  lines.resize (st.st_size);
-  if (myread (desc.get (), &lines[0], lines.size ()) < 0)
-    perror_with_name (symtab_to_filename_for_display (s));
+  time_t file_mtime;
+  std::string lines = read_entire_file (symtab_to_filename_for_display (s),
+					desc.get (), &file_mtime);
 
   time_t mtime = 0;
   if (SYMTAB_OBJFILE (s) != NULL && SYMTAB_OBJFILE (s)->obfd != NULL)
@@ -71,7 +67,7 @@ source_cache::get_plain_source_lines (struct symtab *s,
   else if (exec_bfd)
     mtime = exec_bfd_mtime;
 
-  if (mtime && mtime < st.st_mtime)
+  if (mtime && mtime < file_mtime)
     warning (_("Source file is more recent than executable."));
 
   std::vector<off_t> offsets;
diff --git a/gdb/utils.c b/gdb/utils.c
index 102db28787f..023adfae066 100644
--- a/gdb/utils.c
+++ b/gdb/utils.c
@@ -687,28 +687,6 @@ flush_streams ()
   gdb_stderr->flush ();
 }
 
-/* My replacement for the read system call.
-   Used like `read' but keeps going if `read' returns too soon.  */
-
-int
-myread (int desc, char *addr, int len)
-{
-  int val;
-  int orglen = len;
-
-  while (len > 0)
-    {
-      val = read (desc, addr, len);
-      if (val < 0)
-	return val;
-      if (val == 0)
-	return orglen - len;
-      len -= val;
-      addr += val;
-    }
-  return orglen;
-}
-
 void
 print_spaces (int n, struct ui_file *file)
 {
diff --git a/gdb/utils.h b/gdb/utils.h
index 3434ff1caa2..d0989204128 100644
--- a/gdb/utils.h
+++ b/gdb/utils.h
@@ -540,8 +540,6 @@ void dummy_obstack_deallocate (void *object, void *data);
 extern pid_t wait_to_die_with_timeout (pid_t pid, int *status, int timeout);
 #endif
 
-extern int myread (int, char *, int);
-
 /* Resource limits used by getrlimit and setrlimit.  */
 
 enum resource_limit_kind
diff --git a/gdbsupport/filestuff.cc b/gdbsupport/filestuff.cc
index 179c4258918..0f0a238beb0 100644
--- a/gdbsupport/filestuff.cc
+++ b/gdbsupport/filestuff.cc
@@ -501,3 +501,36 @@ mkdir_recursive (const char *dir)
       component_start = component_end;
     }
 }
+
+/* See filestuff.h.  */
+
+std::string
+read_entire_file (const char *name, int fd, time_t *mtime)
+{
+  struct stat st;
+  if (fstat (fd, &st) < 0)
+    perror_with_name (name);
+  size_t len = st.st_size;
+
+  std::string lines;
+  lines.resize (len);
+  char *addr = &lines[0];
+
+  while (len > 0)
+    {
+      int val = read (fd, addr, len);
+      if (val < 0)
+	perror_with_name (name);
+      if (val == 0)
+	break;
+      len -= val;
+      addr += val;
+    }
+
+  if (mtime != nullptr)
+    *mtime = st.st_mtime;
+
+  /* Just in case we really did end up short.  */
+  lines.resize (st.st_size - len);
+  return lines;
+}
diff --git a/gdbsupport/filestuff.h b/gdbsupport/filestuff.h
index e36936a84ce..84924f462e2 100644
--- a/gdbsupport/filestuff.h
+++ b/gdbsupport/filestuff.h
@@ -139,4 +139,13 @@ extern bool is_regular_file (const char *name, int *errno_ptr);
 
 extern bool mkdir_recursive (const char *dir);
 
+/* Read and return the entire contents of a file.  The file must
+   already be open on FD.  NAME is the file name it is used when
+   reporting errors, which is done by throwing an exception.  The
+   mtime of the file is optionally stored in *MTIME; if MTIME is
+   nullptr, this is ignored.  */
+
+extern std::string read_entire_file (const char *name, int fd,
+				     time_t *mtime = nullptr);
+
 #endif /* COMMON_FILESTUFF_H */
-- 
2.17.2