"break LINENO/*ADDRESS", inline functions and "info break" output

"break LINENO/*ADDRESS", inline functions and "info break" output

While experimenting with the previous patch, I noticed this inconsistency
in GDB's output:

  (gdb) b 32
  Breakpoint 1 at 0x40062f: file inline-break.c, line 32.                  (1)
  (gdb) r
  ....
  Breakpoint 1, func1 (x=1) at inline-break.c:32                           (2)
  32        return x * 23; /* break here */
  (gdb) info breakpoints
  Num     Type           Disp Enb Address    What
  1       breakpoint     keep y   0x40062f   in main at inline-break.c:32  (3)
	  breakpoint already hit 1 time
  (gdb)

Notice that when the breakpoint as set, GDB showed "inline-break.c,
line 32" (1), the same line number that was specified in the command.

When we run to the breakpoint, we present the stop at the same line
number, and correctly show "func1" as the function name (2).

But in "info break" output (3), notice that we say "in main", not "in
func1".

The same thing happens if you set a breakpoint by address.  I.e.:

  (gdb) b *0x40062f
  Breakpoint 2 at 0x40062f: file inline-break.c, line 32.
  (gdb) info breakpoints
  Num     Type           Disp Enb Address            What
  2       breakpoint     keep y   0x000000000040062f in main at inline-break.c:32
   (gdb) r
   ....
  Breakpoint 2, func1 (x=1) at inline-break.c:32
  32        return x * 23; /* break here */

The problem is that the breakpoints were set at an inline function,
but when we set such a breakpoint by line number or address, we don't
record the functions symbol in the sal, and as consequence the
breakpoint location does not have an associated symbol either.

Then, in print_breakpoint_location, if the location does not have a
symbol, we call find_pc_sect_function to find one, and this is what
finds "main", because find_pc_sect_function uses
block_linkage_function:

  /* Return the symbol for the function which contains a specified
     lexical block, described by a struct block BL.  The return value
     will not be an inlined function; the containing function will be
     returned instead.  */

  struct symbol *
  block_linkage_function (const struct block *bl)

To fix this, this commit adds an alternative to find_pc_sect_function
that uses block_containing_function instead:

  /* Return the symbol for the function which contains a specified
     block, described by a struct block BL.  The return value will be
     the closest enclosing function, which might be an inline
     function.  */

  struct symbol *
  block_containing_function (const struct block *bl)

(It seems odd to me that block_linkage_function says "the CONTAINING
function will be returned", and then block_containing_function says it
returns "the closest enclosing function".  Something seems reversed
here.  Still, I've kept the same nomenclature and copied the comments,
so that at least there's consistency.  Maybe we should fix that up
somehow.)

Then I wondered, why make print_breakpoint_location look up the symbol
every time it is called, instead of just always storing the symbol
when the location is created, since the location already stores the
symbol in some cases.  So to find which cases might be missing setting
the symbol in the sal which is used to create the breakpoint location,
I added an assertion to print_breakpoint_location, and ran the
testsuite.  That caught a few places, unsurprisingly:

 - setting a breakpoint by line number
 - setting a breapoint by address
 - ifunc resolving

Those are all fixed by this commit.  I decided not to add the
assertion to block_linkage_function and leave the existing "if (sym)"
check in place, because it's plausible that we have symtabs with line
info but no symbols.  I.e., that would not be a GDB bug, but
a peculiarity of debug info input.

gdb/ChangeLog:
2018-06-29  Pedro Alves  <palves@redhat.com>

	* blockframe.c (find_pc_sect_containing_function): New function.
	* breakpoint.c (print_breakpoint_location): Don't call
	find_pc_sect_function.
	* linespec.c (create_sals_line_offset): Record the location's
	symbol in the sal.
	* linespec.c (convert_address_location_to_sals): Fill in sal's
	symbol with find_pc_sect_containing_function.
	* symtab.c (find_function_start_sal): Rename to ...
	(find_function_start_sal_1): ... this.
	(find_function_start_sal): Reimplement as wrapper around
	find_function_start_sal_1, and use
	find_pc_sect_containing_function to fill in the sal's symbol.
	(find_function_start_sal(symbol*, bool)): Adjust.
	* symtab.h (find_pc_function, find_pc_sect_function): Adjust
	comments.
	(find_pc_sect_containing_function): Declare.

gdb/testsuite/ChangeLog:
2018-06-29  Pedro Alves  <palves@redhat.com>

	* gdb.opt/inline-break.exp (line number, address): Add "info
	break" tests.