[PATCH v2] GDB: Fix the overflow in addr_is_displayed()

[Shahab Vahedi]

From: Shahab Vahedi <shahab@synopsys.com>

In a corner case scenario, where the height of the assembly TUI is
bigger than the number of instructions in the whole program, GDB
dumps core. The problem roots in this condition check:

  int i = 0;
  while (i < content. size() - threshold ...) {
    ... content[i] ...
  }

"threshold" is 2 and there are times that "content. size()" is 0.
This results into an overflow and the loop is entered whereas it
should have been skipped.

This has been discussed at length in bug 25345:
  https://sourceware.org/bugzilla/show_bug.cgi?id=25345

As a bonus, a few trailing spaces are also removed.

gdb/ChangeLog:
2020-01-04  Shahab Vahedi  <shahab@synopsys.com>
        * tui/tui-disasm.c (tui_disasm_window::addr_is_displayed):
        Treat "content.size ()" as "int" to avoid overflow.
        * tui/tui-disasm.c: Remove trailing spaces.
---
 gdb/tui/tui-disasm.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/gdb/tui/tui-disasm.c b/gdb/tui/tui-disasm.c
index c72b50730b0..68744cc61e3 100644
--- a/gdb/tui/tui-disasm.c
+++ b/gdb/tui/tui-disasm.c
@@ -43,7 +43,7 @@
 
 #include "gdb_curses.h"
 
-struct tui_asm_line 
+struct tui_asm_line
 {
   CORE_ADDR addr;
   std::string addr_string;
@@ -150,7 +150,7 @@ tui_find_disassembly_address (struct gdbarch *gdbarch, CORE_ADDR pc, int from)
       CORE_ADDR last_addr;
       int pos;
       struct bound_minimal_symbol msymbol;
-              
+
       /* Find backward an address which is a symbol and for which
          disassembling from that address will fill completely the
          window.  */
@@ -176,7 +176,7 @@ tui_find_disassembly_address (struct gdbarch *gdbarch, CORE_ADDR pc, int from)
         do
           {
             CORE_ADDR next_addr;
-                 
+
             pos++;
             if (pos >= max_lines)
               pos = 0;
@@ -349,10 +349,10 @@ bool
 tui_disasm_window::addr_is_displayed (CORE_ADDR addr) const
 {
   bool is_displayed = false;
-  int threshold = SCROLL_THRESHOLD;
+  int nr_of_lines = (int) content. size() - SCROLL_THRESHOLD;
 
   int i = 0;
-  while (i < content.size () - threshold && !is_displayed)
+  while (i < nr_of_lines && !is_displayed)
     {
       is_displayed
 	= (content[i].line_or_addr.loa == LOA_ADDRESS
-- 
2.24.1