gdbsupport: Adapt construct_inferior_arguments

Allow construct_inferior_arguments to handle zero args
and have it return a std::string, similar to how
stringify_argv in gdbsupport/common-utils does.

Also, add a const qualifier for the second parameter,
since it is only read, not written to.

The intention is to replace existing uses of
stringify_argv by construct_inferior_arguments
in a subsequent step, since construct_inferior_arguments
properly handles special characters, while stringify_argv
doesn't.

gdbsupport/ChangeLog:

	* common-inferior.cc, common-inferior.h (construct_inferior_arguments):
	Adapt to handle zero args and return a std::string.
	Adapt call site.

Change-Id: I126c4390a1018c7527b0b8fd545252ab8a5a7adc

3 files changed, 29 insertions, 44 deletions

diff --git a/gdbsupport/ChangeLog b/gdbsupport/ChangeLog
index 4f72c7d..67dcdee 100644
--- a/gdbsupport/ChangeLog
+++ b/gdbsupport/ChangeLog
@@ -1,5 +1,11 @@
 2020-05-25  Michael Weghorn  <m.weghorn@posteo.de>
 
+	* common-inferior.cc, common-inferior.h (construct_inferior_arguments):
+	Adapt to handle zero args and return a std::string.
+	Adapt call site.
+
+2020-05-25  Michael Weghorn  <m.weghorn@posteo.de>
+
 	* common-inferior.h, common-inferior.cc: (construct_inferior_arguments):
 	Move function here from gdb/infcmd.c, gdb/inferior.h
 
diff --git a/gdbsupport/common-inferior.cc b/gdbsupport/common-inferior.cc
index a7d631f..aa8be14 100644
--- a/gdbsupport/common-inferior.cc
+++ b/gdbsupport/common-inferior.cc
@@ -27,15 +27,12 @@ bool startup_with_shell = true;
 
 /* See common-inferior.h.  */
 
-char *
-construct_inferior_arguments (int argc, char **argv)
+std::string
+construct_inferior_arguments (int argc, char * const *argv)
 {
-  char *result;
+  gdb_assert (argc >= 0);
 
-  /* ARGC should always be at least 1, but we double check this
-     here.  This is also needed to silence -Werror-stringop
-     warnings.  */
-  gdb_assert (argc > 0);
+  std::string result;
 
   if (startup_with_shell)
     {
@@ -51,49 +48,38 @@ construct_inferior_arguments (int argc, char **argv)
       static const char special[] = "\"!#$&*()\\|[]{}<>?'`~^; \t\n";
       static const char quote = '\'';
 #endif
-      int i;
-      int length = 0;
-      char *out, *cp;
-
-      /* We over-compute the size.  It shouldn't matter.  */
-      for (i = 0; i < argc; ++i)
-	length += 3 * strlen (argv[i]) + 1 + 2 * (argv[i][0] == '\0');
-
-      result = (char *) xmalloc (length);
-      out = result;
-
-      for (i = 0; i < argc; ++i)
+      for (int i = 0; i < argc; ++i)
 	{
 	  if (i > 0)
-	    *out++ = ' ';
+	    result += ' ';
 
 	  /* Need to handle empty arguments specially.  */
 	  if (argv[i][0] == '\0')
 	    {
-	      *out++ = quote;
-	      *out++ = quote;
+	      result += quote;
+	      result += quote;
 	    }
 	  else
 	    {
 #ifdef __MINGW32__
-	      int quoted = 0;
+	      bool quoted = false;
 
 	      if (strpbrk (argv[i], special))
 		{
-		  quoted = 1;
-		  *out++ = quote;
+		  quoted = true;
+		  result += quote;
 		}
 #endif
-	      for (cp = argv[i]; *cp; ++cp)
+	      for (char *cp = argv[i]; *cp; ++cp)
 		{
 		  if (*cp == '\n')
 		    {
 		      /* A newline cannot be quoted with a backslash (it
 			 just disappears), only by putting it inside
 			 quotes.  */
-		      *out++ = quote;
-		      *out++ = '\n';
-		      *out++ = quote;
+		      result += quote;
+		      result += '\n';
+		      result += quote;
 		    }
 		  else
 		    {
@@ -102,26 +88,22 @@ construct_inferior_arguments (int argc, char **argv)
 #else
 		      if (strchr (special, *cp) != NULL)
 #endif
-			*out++ = '\\';
-		      *out++ = *cp;
+			result += '\\';
+		      result += *cp;
 		    }
 		}
 #ifdef __MINGW32__
 	      if (quoted)
-		*out++ = quote;
+		result += quote;
 #endif
 	    }
 	}
-      *out = '\0';
     }
   else
     {
       /* In this case we can't handle arguments that contain spaces,
 	 tabs, or newlines -- see breakup_args().  */
-      int i;
-      int length = 0;
-
-      for (i = 0; i < argc; ++i)
+      for (int i = 0; i < argc; ++i)
 	{
 	  char *cp = strchr (argv[i], ' ');
 	  if (cp == NULL)
@@ -131,16 +113,13 @@ construct_inferior_arguments (int argc, char **argv)
 	  if (cp != NULL)
 	    error (_("can't handle command-line "
 		     "argument containing whitespace"));
-	  length += strlen (argv[i]) + 1;
 	}
 
-      result = (char *) xmalloc (length);
-      result[0] = '\0';
-      for (i = 0; i < argc; ++i)
+      for (int i = 0; i < argc; ++i)
 	{
 	  if (i > 0)
-	    strcat (result, " ");
-	  strcat (result, argv[i]);
+	    result += " ";
+	  result += argv[i];
 	}
     }
 
diff --git a/gdbsupport/common-inferior.h b/gdbsupport/common-inferior.h
index ee87bc7..5e9fc8b 100644
--- a/gdbsupport/common-inferior.h
+++ b/gdbsupport/common-inferior.h
@@ -60,6 +60,6 @@ extern bool startup_with_shell;
 
 /* Compute command-line string given argument vector. This does the
    same shell processing as fork_inferior.  */
-extern char *construct_inferior_arguments (int, char **);
+extern std::string construct_inferior_arguments (int, char * const *);
 
 #endif /* COMMON_COMMON_INFERIOR_H */