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[RFA/commit/Win64] Remove new extra leading underscore in symbol name

For any Ada program, the debugger no longer finds the right routine as
the main subprogram when using the "start" command.  For instance:

    % gdb simple_main
    (gdb) start
    Temporary breakpoint 1, main (argc=1, argv=(system.address) 0x232470, [...]

The expected behavior is to stop in the Ada main program:

    (gdb) start
    Temporary breakpoint 1, simple_main () at simple_main.adb:4
    4           simple.test_simple;

The problem was introduced, I believe, by a patch in bfd causing
the names in the symbol table to now have a leading underscore:

    Adjust calling convention of x64 windows to non-leading underscore

In the case of the "start" command, the search for the name of the
main subprogram requires GDB to find the __gnat_ada_main_program_name
symbol.  But since the patch above got applied, GDB now sees that
(minimal) symbol as ___gnat_ada_main_program_name (extra leading

Other consequences of that change of behavior:

  - Ada tasking support is broken, since it relies on other known
    symbol names;

  - minimal symbol and symbols from debug info has non-matching names;
    I would think that some parts of GDB's code make the assumption
    that these names match, at least for C, but I might be unnecessarily

This patch changes the COFF reader such that, for COFF/PE64, we discard
the leading underscore.

2010-06-17  Joel Brobecker  <>

        * coffread.c (getsymname): Skip the leading underscore on pe64.

Tested on x64-windows with AdaCore's testsuite (we do a MinGW build).
I'd like to commit a fix before 7.2.

Kai's input would be greatly appreciated, as he probably knows Windows
a thousand times better than I do.

 gdb/coffread.c |   14 ++++++++++++++
 1 files changed, 14 insertions(+), 0 deletions(-)

diff --git a/gdb/coffread.c b/gdb/coffread.c
index 52417b2..4ab0640 100644
--- a/gdb/coffread.c
+++ b/gdb/coffread.c
@@ -1256,6 +1256,9 @@ getsymname (struct internal_syment *symbol_entry)
   static char buffer[SYMNMLEN + 1];
   char *result;
+  const char *target = bfd_get_target (symfile_bfd);
+  const int is_pe64 = (strcmp (target, "pe-x86-64") == 0
+                       || strcmp (target, "pei-x86-64") == 0);
   if (symbol_entry->_n._n_n._n_zeroes == 0)
@@ -1269,6 +1272,17 @@ getsymname (struct internal_syment *symbol_entry)
       buffer[SYMNMLEN] = '\0';
       result = buffer;
+  /* On x64-windows, an extra leading underscore is usually added to
+     the symbol name.  However, the name provided in the associated
+     debug information does not include that underscore.  So remove it
+     now, to make the two names match.
+     This is also useful for code that searches the minimal symbols
+     for a specific symbol whose name should be target-independent.  */
+  if (is_pe64 && result[0] == '_')
+    result++;
   return result;

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