* [PATCH] Allow cast of 128-bit integer to pointer
@ 2023-11-25 2:25 Tom Tromey
2023-12-08 15:15 ` Tom Tromey
0 siblings, 1 reply; 2+ messages in thread
From: Tom Tromey @ 2023-11-25 2:25 UTC (permalink / raw)
To: gdb-patches; +Cc: Tom Tromey
PR rust/31082 points out that casting a 128-bit integer to a pointer
will fail. This happens because a case in value_cast was not
converted to use GMP.
This patch fixes the problem. I am not really sure that testing
against the negative value here makes sense, but I opted to just
preserve the existing behavior rather than change it.
Regression tested on x86-64 Fedora 38.
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=31082
---
gdb/gmp-utils.h | 15 ++++++++++++++-
gdb/testsuite/gdb.rust/expr.exp | 5 +++++
gdb/valops.c | 14 ++++++--------
3 files changed, 25 insertions(+), 9 deletions(-)
diff --git a/gdb/gmp-utils.h b/gdb/gmp-utils.h
index a5c27feb59f..52052e30d26 100644
--- a/gdb/gmp-utils.h
+++ b/gdb/gmp-utils.h
@@ -251,19 +251,32 @@ struct gdb_mpz
return result;
}
+ gdb_mpz operator- () const
+ {
+ gdb_mpz result;
+ mpz_neg (result.m_val, m_val);
+ return result;
+ }
+
gdb_mpz &operator<<= (unsigned long nbits)
{
mpz_mul_2exp (m_val, m_val, nbits);
return *this;
}
- gdb_mpz operator<< (unsigned long nbits) const
+ gdb_mpz operator<< (unsigned long nbits) const &
{
gdb_mpz result;
mpz_mul_2exp (result.m_val, m_val, nbits);
return result;
}
+ gdb_mpz operator<< (unsigned long nbits) &&
+ {
+ mpz_mul_2exp (m_val, m_val, nbits);
+ return *this;
+ }
+
gdb_mpz operator>> (unsigned long nbits) const
{
gdb_mpz result;
diff --git a/gdb/testsuite/gdb.rust/expr.exp b/gdb/testsuite/gdb.rust/expr.exp
index ce2cce2677c..cec3c1fccd8 100644
--- a/gdb/testsuite/gdb.rust/expr.exp
+++ b/gdb/testsuite/gdb.rust/expr.exp
@@ -169,3 +169,8 @@ gdb_test "with debug expression 1 -- print \"foo\"" \
" Constant: 0" \
"evaluation of this expression requires the target program to be active"] \
"print a string with expression debug turned on"
+
+# PR rust/31082 - truncating to a pointer would fail. Depending on
+# the default host architecture, this may or may not print a warning.
+gdb_test "print (0xffffffd00000009a as *mut u64)" \
+ "(warning: value truncated\[\r\n\]+)?.* = \\(\\*mut u64\\) $hex"
diff --git a/gdb/valops.c b/gdb/valops.c
index a8760ccf3e4..bf376921ca3 100644
--- a/gdb/valops.c
+++ b/gdb/valops.c
@@ -603,15 +603,13 @@ value_cast (struct type *type, struct value *arg2)
pointers and four byte addresses. */
int addr_bit = gdbarch_addr_bit (type2->arch ());
- LONGEST longest = value_as_long (arg2);
+ gdb_mpz longest = value_as_mpz (arg2);
- if (addr_bit < sizeof (LONGEST) * HOST_CHAR_BIT)
- {
- if (longest >= ((LONGEST) 1 << addr_bit)
- || longest <= -((LONGEST) 1 << addr_bit))
- warning (_("value truncated"));
- }
- return value_from_longest (to_type, longest);
+ gdb_mpz addr_val = gdb_mpz (1) << addr_bit;
+ if (longest >= addr_val || longest <= -addr_val)
+ warning (_("value truncated"));
+
+ return value_from_mpz (to_type, longest);
}
else if (code1 == TYPE_CODE_METHODPTR && code2 == TYPE_CODE_INT
&& value_as_long (arg2) == 0)
--
2.41.0
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [PATCH] Allow cast of 128-bit integer to pointer
2023-11-25 2:25 [PATCH] Allow cast of 128-bit integer to pointer Tom Tromey
@ 2023-12-08 15:15 ` Tom Tromey
0 siblings, 0 replies; 2+ messages in thread
From: Tom Tromey @ 2023-12-08 15:15 UTC (permalink / raw)
To: Tom Tromey; +Cc: gdb-patches
>>>>> "Tom" == Tom Tromey <tom@tromey.com> writes:
Tom> PR rust/31082 points out that casting a 128-bit integer to a pointer
Tom> will fail. This happens because a case in value_cast was not
Tom> converted to use GMP.
Tom> This patch fixes the problem. I am not really sure that testing
Tom> against the negative value here makes sense, but I opted to just
Tom> preserve the existing behavior rather than change it.
I'm checking this in.
Tom
^ permalink raw reply [flat|nested] 2+ messages in thread
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