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Allow cast of 128-bit integer to pointer

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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
This commit is contained in:
Tom Tromey 2023-11-24 12:10:53 -07:00
parent 703adbb1f9
commit 44671f3f7f
3 changed files with 25 additions and 9 deletions
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15
gdb/gmp-utils.h
View file

@ -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;

5
gdb/testsuite/gdb.rust/expr.exp
View file

@ -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"

14
gdb/valops.c
View file

@ -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)