gdb: use std::string instead of a fixed size buffer

The 'section' command uses a fixed size buffer into which a section
name is copied.  This commit replaces this with a use of std::string
so we can now display very long section names.

The expected results of one test need to be updated.

gdb/ChangeLog:

	* exec.c (set_section_command): Move variable declarations into
	the function body, and use std::string instead of a fixed size
	buffer.

gdb/testsuite/ChangeLog:

	* gdb.base/sect-cmd.exp: Update expected results.

gdb/ChangeLog

@@ -1,3 +1,9 @@
+2021-02-24  Andrew Burgess  <andrew.burgess@embecosm.com>
+
+	* exec.c (set_section_command): Move variable declarations into
+	the function body, and use std::string instead of a fixed size
+	buffer.
+
 2021-02-24  Andrew Burgess  <andrew.burgess@embecosm.com>
 
 	* exec.c (exec_target::get_section_table): Delete member function.

gdb/exec.c

@@ -989,27 +989,23 @@ static void
 set_section_command (const char *args, int from_tty)
 {
   const char *secname;
-  unsigned seclen;
-  unsigned long secaddr;
-  char secprint[100];
-  long offset;
 
   if (args == 0)
     error (_("Must specify section name and its virtual address"));
 
   /* Parse out section name.  */
   for (secname = args; !isspace (*args); args++);
-  seclen = args - secname;
+  unsigned seclen = args - secname;
 
   /* Parse out new virtual address.  */
-  secaddr = parse_and_eval_address (args);
+  CORE_ADDR secaddr = parse_and_eval_address (args);
 
   for (target_section &p : current_program_space->target_sections ())
     {
       if (!strncmp (secname, bfd_section_name (p.the_bfd_section), seclen)
 	  && bfd_section_name (p.the_bfd_section)[seclen] == '\0')
 	{
-	  offset = secaddr - p.addr;
+	  long offset = secaddr - p.addr;
 	  p.addr += offset;
 	  p.endaddr += offset;
 	  if (from_tty)
@@ -1017,11 +1013,9 @@ set_section_command (const char *args, int from_tty)
 	  return;
 	}
     }
-  if (seclen >= sizeof (secprint))
-    seclen = sizeof (secprint) - 1;
-  strncpy (secprint, secname, seclen);
-  secprint[seclen] = '\0';
-  error (_("Section %s not found"), secprint);
+
+  std::string secprint (secname, seclen);
+  error (_("Section %s not found"), secprint.c_str ());
 }
 
 /* If we can find a section in FILENAME with BFD index INDEX, adjust

gdb/testsuite/ChangeLog

@@ -1,3 +1,7 @@
+2021-02-24  Andrew Burgess  <andrew.burgess@embecosm.com>
+
+	* gdb.base/sect-cmd.exp: Update expected results.
+
 2021-02-24  Andrew Burgess  <andrew.burgess@embecosm.com>
 
 	* gdb.base/sect-cmd.exp: Rewrite using modern testsuite

gdb/testsuite/gdb.base/sect-cmd.exp

@@ -79,14 +79,16 @@ gdb_test_multiple "section FOOBARBAZ 0x1234" "" {
     }
 }
 
-# We "happen to know" that GDB uses a fixed size character buffer to
-# parse the section name into, and the buffer is declared to be 100
-# characters in length.  Verify that GDB gracefully handles section
-# names longer than that.  (The section is also non-existent.)
+# Check that GDB can still print the error message when the section
+# name is very long.  It used to be the case that GDB could only print
+# (up to) 100 character section names in this error message, but that
+# is no longer the case.
 #
-gdb_test_multiple "section A234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123 0x1234" \
+set long_sect_name \
+    "A234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123"
+gdb_test_multiple "section $long_sect_name 0x1234" \
     "non-existent too-long section disallowed" {
-	-re -wrap "Section A23456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789 not found" {
+	-re -wrap "Section $long_sect_name not found" {
 	    pass $gdb_test_name
 	}
     }