[binutils-gdb] gdb: remove assertion in psymbol_functions::expand_symtabs_matching

[Simon Marchi <simark@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=cb25fdbb76e41d9c02fe86009fc8a3ecf8737c9a

commit cb25fdbb76e41d9c02fe86009fc8a3ecf8737c9a
Author: Simon Marchi <simon.marchi@polymtl.ca>
Date:   Thu Mar 31 16:38:33 2022 -0400

    gdb: remove assertion in psymbol_functions::expand_symtabs_matching
    
    psymtab_to_symtab is documented as possibly returning nullptr, if the
    primary symtab of the partial symtab has no symbols.  However,
    psymbol_functions::expand_symtabs_matching asserts that the result of
    psymtab_to_symtab as non-nullptr.
    
    I caught this assert by trying the CTF symbol reader on a library I
    built with -gctf:
    
        $ ./gdb --data-directory=data-directory /tmp/babeltrace-ctf/src/lib/.libs/libbabeltrace2.so.0.0.0
        ...
        Reading symbols from /tmp/babeltrace-ctf/src/lib/.libs/libbabeltrace2.so.0.0.0...
        (gdb) maintenance expand-symtabs
        /home/simark/src/binutils-gdb/gdb/psymtab.c:1142: internal-error: expand_symtabs_matching: Assertion `symtab != nullptr' failed.
    
    The "symtab" in question is:
    
        $  readelf --ctf=.ctf /tmp/babeltrace-ctf/src/lib/.libs/libbabeltrace2.so.0.0.0
        ...
        CTF archive member: /home/simark/src/babeltrace/src/lib/graph/component-descriptor-set.c:
    
          Header:
            Magic number: 0xdff2
            Version: 4 (CTF_VERSION_3)
            Flags: 0xe (CTF_F_NEWFUNCINFO, CTF_F_IDXSORTED, CTF_F_DYNSTR)
            Parent name: .ctf
            Compilation unit name: /home/simark/src/babeltrace/src/lib/graph/component-descriptor-set.c
            Type section:       0x0 -- 0x13 (0x14 bytes)
            String section:     0x14 -- 0x5f (0x4c bytes)
    
          Labels:
    
          Data objects:
    
          Function objects:
    
          Variables:
    
          Types:
            0x80000001: (kind 5) bt_bool (*) (const bt_value *) (aligned at 0x8)
    
          Strings:
            0x0:
            0x1: .ctf
            0x6: /home/simark/src/babeltrace/src/lib/graph/component-descriptor-set.c
    
    It contains a single type, and it is skipped by ctf_add_type_cb, because
    an identical type was already seen earlier in this objfile.  As a
    result, no compunit_symtab is created.
    
    Change psymbol_functions::expand_symtabs_matching to expect that
    psymtab_to_symtab can return nullptr.
    
    Another possibility would be to make the CTF symbol reader always create
    a compunit_symtab, even if there are no symbols in it (like the DWARF
    parser does), but so far I don't see any advantage in doing so.
    
    Change-Id: Ic43c38202c838a5eb87630ed1fd61d33528164f4

Diff:
---
 gdb/psymtab.c | 9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/gdb/psymtab.c b/gdb/psymtab.c
index b31ce877b62..a26ecd0b4e5 100644
--- a/gdb/psymtab.c
+++ b/gdb/psymtab.c
@@ -1136,13 +1136,10 @@ psymbol_functions::expand_symtabs_matching
 					  *psym_lookup_name,
 					  symbol_matcher))
 	{
-	  struct compunit_symtab *symtab =
-	    psymtab_to_symtab (objfile, ps);
+	  compunit_symtab *cust = psymtab_to_symtab (objfile, ps);
 
-	  gdb_assert (symtab != nullptr);
-
-	  if (expansion_notify != NULL)
-	    if (!expansion_notify (symtab))
+	  if (cust != nullptr && expansion_notify != nullptr)
+	    if (!expansion_notify (cust))
 	      return false;
 	}
     }