From a6800d9c8145f25001dd39afc3571e3350573e81 Mon Sep 17 00:00:00 2001 From: Tom de Vries Date: Mon, 6 May 2024 14:23:25 +0200 Subject: [PATCH] [gdb/exp] Redo cast handling for indirection In commit ed8fd0a342f ("[gdb/exp] Fix cast handling for indirection"), I introduced the behaviour that even though we have: ... (gdb) p *a_loc () 'a_loc' has unknown return type; cast the call to its declared return type ... we get: ... (gdb) p (char)*a_loc () $1 = 97 'a' ... In other words, the unknown return type of a_loc is inferred from the cast, effectually evaluating: ... (gdb) p (char)*(char *)a_loc () ... This is convient for the case that errno is defined as: ... #define errno (*__errno_location ()) ... and the return type of __errno_location is unknown but the macro definition is known, such that we can use: ... (gdb) p (int)errno ... instead of ... (gdb) p *(int *)__errno_location () ... However, as Pedro has pointed out in post-commit review [1], this makes it harder to reason about the semantics of an expression. For instance, this: ... (gdb) p (long long)*a_loc ()" ... would be evaluated without debug info as: ... (gdb) p (long long)*(long long *)a_loc ()" ... but with debug info as: ... (gdb) p (long long)*(char *)a_loc ()" ... Fix this by instead simply erroring out for this case: ... (gdb) p (char)*a_loc () 'a_loc' has unknown return type; cast the call to its declared return type ... Tested on x86_64-linux. Approved-By: Pedro Alves [1] https://sourceware.org/pipermail/gdb-patches/2024-May/208821.html --- gdb/testsuite/gdb.base/cast-indirection.exp | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/gdb/testsuite/gdb.base/cast-indirection.exp b/gdb/testsuite/gdb.base/cast-indirection.exp index f1fe4302d27..7b9b5a5d677 100644 --- a/gdb/testsuite/gdb.base/cast-indirection.exp +++ b/gdb/testsuite/gdb.base/cast-indirection.exp @@ -13,7 +13,7 @@ # You should have received a copy of the GNU General Public License # along with this program. If not, see . -# Check that "p (char)*a_loc ()" is handled as "p (char)*(char *)a_loc ()". +# Check that "p (char)*a_loc ()" is handled correctly. standard_testfile base-commit: fc73000faa1798573090994167b7e2d451c211db -- 2.35.3