[PATCH v2 2/2] compile: Add 'set compile-gcc'

[Jan Kratochvil <jan dot kratochvil at redhat dot com>]

Hi,

as discussed in
	How to use compile & execute function in GDB
	https://sourceware.org/ml/gdb/2015-04/msg00026.html

GDB currently searches for /usr/bin/ARCH-OS-gcc and chooses one but one cannot
override which one.

This patch does not change the libcc1 API as it overloads the triplet_regexp
parameter of GCC's set_arguments.  GCC decides on the meaning of the
triplet_regexp parameter according to the success of:

+  if (access (triplet_regexp, X_OK) == 0)


Jan


gdb/ChangeLog
2015-04-21  Jan Kratochvil  <jan.kratochvil@redhat.com>

	* compile/compile.c (compile_gcc, show_compile_gcc): New.
	(compile_to_object): Implement compile_gcc.
	(_initialize_compile): Install "set compile-gcc".  Initialize
	compile_gcc.

gdb/doc/ChangeLog
2015-04-21  Jan Kratochvil  <jan.kratochvil@redhat.com>

	* doc/gdb.texinfo (Compiling and Injecting Code): Add to subsection
	Compiler search for the compile command descriptions of set
	compile-gcc and show compile-gcc.

include/ChangeLog
2015-04-21  Jan Kratochvil  <jan.kratochvil@redhat.com>

	* gcc-interface.h (enum gcc_base_api_version): Add comment to
	GCC_FE_VERSION_1.
	(struct gcc_base_vtable): Describe triplet_regexp parameter overload
	for set_arguments.
---
 gdb/compile/compile.c   |   40 +++++++++++++++++++++++++++++++++-------
 gdb/doc/gdb.texinfo     |   33 ++++++++++++++++++++++++++++-----
 include/gcc-interface.h |    7 +++++--
 3 files changed, 66 insertions(+), 14 deletions(-)

diff --git a/gdb/compile/compile.c b/gdb/compile/compile.c
index 7f4c11d..c5267ba 100644
--- a/gdb/compile/compile.c
+++ b/gdb/compile/compile.c
@@ -299,6 +299,19 @@ append_args (int *argcp, char ***argvp, int argc, char **argv)
   (*argvp)[(*argcp)] = NULL;
 }
 
+/* String for 'set compile-gcc' and 'show compile-gcc'.  */
+static char *compile_gcc;
+
+/* Implement 'show compile-gcc'.  */
+
+static void
+show_compile_gcc (struct ui_file *file, int from_tty,
+		  struct cmd_list_element *c, const char *value)
+{
+  fprintf_filtered (file, _("Compile command GCC driver filename is \"%s\".\n"),
+		    value);
+}
+
 /* Return DW_AT_producer parsed for get_selected_frame () (if any).
    Return NULL otherwise.
 
@@ -430,8 +443,6 @@ compile_to_object (struct command_line *cmd, char *cmd_string,
   int ok;
   FILE *src;
   struct gdbarch *gdbarch = get_current_arch ();
-  const char *os_rx;
-  const char *arch_rx;
   char *triplet_rx;
   char *error_message;
 
@@ -481,12 +492,17 @@ compile_to_object (struct command_line *cmd, char *cmd_string,
   if (compile_debug)
     fprintf_unfiltered (gdb_stdout, "debug output:\n\n%s", code);
 
-  os_rx = osabi_triplet_regexp (gdbarch_osabi (gdbarch));
-  arch_rx = gdbarch_gnu_triplet_regexp (gdbarch);
+  if (compile_gcc[0] != 0)
+    triplet_rx = compile_gcc;
+  else
+    {
+      const char *os_rx = osabi_triplet_regexp (gdbarch_osabi (gdbarch));
+      const char *arch_rx = gdbarch_gnu_triplet_regexp (gdbarch);
 
-  /* Allow triplets with or without vendor set.  */
-  triplet_rx = concat (arch_rx, "(-[^-]*)?-", os_rx, (char *) NULL);
-  make_cleanup (xfree, triplet_rx);
+      /* Allow triplets with or without vendor set.  */
+      triplet_rx = concat (arch_rx, "(-[^-]*)?-", os_rx, (char *) NULL);
+      make_cleanup (xfree, triplet_rx);
+    }
 
   /* Set compiler command-line arguments.  */
   get_args (compiler, gdbarch, &argc, &argv);
@@ -688,4 +704,14 @@ String quoting is parsed like in shell, for example:\n\
 			 " -fno-stack-protector"
   );
   set_compile_args (compile_args, 0, NULL);
+
+  add_setshow_string_cmd ("compile-gcc", class_support,
+			  &compile_gcc,
+			  _("Set compile command GCC driver filename"),
+			  _("Show compile command GCC driver filename"),
+			  _("\
+It should be absolute pathname to the gcc executable.\n\
+If empty the default target triplet will be searched in $PATH."),
+			  NULL, show_compile_gcc, &setlist, &showlist);
+  compile_gcc = xstrdup ("");
 }
diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index 0410702..8f3777d 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -17437,11 +17437,13 @@ will print to the console.
 
 @value{GDBN} needs to find @value{NGCC} for the inferior being debugged which
 may not be obvious for remote targets of different architecture than where
-@value{GDBN} is running.  Environment variable @code{PATH} (@code{PATH} from
-shell that executed @value{GDBN}, not the one set by @value{GDBN}
-command @code{set environment}).  @xref{Environment}.  @code{PATH} on
-@value{GDBN} host is searched for @value{NGCC} binary matching the
-target architecture and operating system.
+@value{GDBN} is running.  By default the environment variable
+@code{PATH} (@code{PATH} from shell that executed @value{GDBN}, not the
+one set by @value{GDBN} command @code{set environment}).
+@xref{Environment}.  @code{PATH} on @value{GDBN} host is searched for
+@value{NGCC} binary matching the target architecture and operating
+system.  This search can be overriden by @code{set compile-gcc} @value{GDBN}
+command below.
 
 Specifically @code{PATH} is searched for binaries matching regular expression
 @code{@var{arch}(-[^-]*)?-@var{os}-gcc} according to the inferior target being
@@ -17451,6 +17453,27 @@ example both @code{i386} and @code{x86_64} targets look for pattern
 for pattern @code{s390x?}.  @var{os} is currently supported only for
 pattern @code{linux(-gnu)?}.
 
+Besides the compiler driver @value{GDBN} needs also shared library
+@file{libcc1.so}.  It is searched in default shared library search path
+(overridable with usual environment variable @code{LD_LIBRARY_PATH}),
+unrelated to @code{PATH} or @code{set compile-gcc} settings.  Contrary to it
+@file{libcc1plugin.so} is found according to the installation of the found
+compiler --- as possibly specified by the @code{set compile-gcc} command.
+
+@table @code
+@item set compile-gcc
+@cindex compile command driver filename override
+Set compilation command used for compiling and injecting code with the
+@code{compile} commands.  If this option is not set (it is set to
+an empty string), the search described above will occur --- that is the
+default.
+
+@item show compile-gcc
+Displays the current compile command @value{NGCC} driver filename.
+If set, it is the main command @code{gcc}, found usually for example
+under name @code{x86_64-linux-gnu-gcc}.
+@end table
+
 @node GDB Files
 @chapter @value{GDBN} Files
 
diff --git a/include/gcc-interface.h b/include/gcc-interface.h
index c11b7a1..81925b1 100644
--- a/include/gcc-interface.h
+++ b/include/gcc-interface.h
@@ -46,7 +46,9 @@ enum gcc_base_api_version
 {
   GCC_FE_VERSION_0 = 0,
 
-  /* Parameter verbose has been moved from compile to set_arguments.  */
+  /* Parameter verbose has been moved from compile to set_arguments.
+     Parameter triplet_regexp of set_arguments can be also gcc driver
+     executable.  */
   GCC_FE_VERSION_1 = 1,
 };
 
@@ -104,7 +106,8 @@ struct gcc_base_vtable
 
   /* Set the compiler's command-line options for the next compilation.
      TRIPLET_REGEXP is a regular expression that is used to match the
-     configury triplet prefix to the compiler.
+     configury triplet prefix to the compiler; TRIPLET_REGEXP can be
+     also absolute filename  to the computer.
      The arguments are copied by GCC.  ARGV need not be
      NULL-terminated.  The arguments must be set separately for each
      compilation; that is, after a compile is requested, the