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reject negative unnamed-type numbers in ParseUnnamedTypeName #2115

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reject negative unnamed-type numbers in ParseUnnamedTypeName #2115

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2 changes: 2 additions & 0 deletions absl/debugging/internal/demangle.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -973,6 +973,7 @@ static bool ParseUnnamedTypeName(State *state) {

// Unnamed type local to function or class.
if (ParseTwoCharToken(state, "Ut") && Optional(ParseNumber(state, &which)) &&
which >= -1 && // Don't print garbage.
which <= std::numeric_limits<int>::max() - 2 && // Don't overflow.
ParseOneCharToken(state, '_')) {
MaybeAppend(state, "{unnamed type#");
Expand All @@ -988,6 +989,7 @@ static bool ParseUnnamedTypeName(State *state) {
ZeroOrMore(ParseTemplateParamDecl, state) &&
OneOrMore(ParseType, state) && RestoreAppend(state, copy.append) &&
ParseOneCharToken(state, 'E') && Optional(ParseNumber(state, &which)) &&
which >= -1 && // Don't print garbage.
which <= std::numeric_limits<int>::max() - 2 && // Don't overflow.
ParseOneCharToken(state, '_')) {
MaybeAppend(state, "{lambda()#");
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25 changes: 25 additions & 0 deletions absl/debugging/internal/demangle_test.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -471,6 +471,31 @@ TEST(Demangle, AvoidSignedOverflowForUnfortunateParameterNumbers) {
EXPECT_STREQ(tmp, "S::f()::{default arg#1}::{lambda()#1}::operator()()");
}

TEST(Demangle, NegativeUnnamedTypeNumbers) {
char tmp[100];

// An omitted <number> denotes index 1 and is left as the -1 sentinel.
ASSERT_TRUE(Demangle("_ZUt_", tmp, sizeof(tmp)));
EXPECT_STREQ(tmp, "{unnamed type#1}");
ASSERT_TRUE(Demangle("_ZUlvE_", tmp, sizeof(tmp)));
EXPECT_STREQ(tmp, "{lambda()#1}");

// Reject an explicitly negative <number>. Left unstrained, <number> + 2 is
// negative, and MaybeAppendDecimal emits (val % 10) + '0' per digit, which
// for a negative val yields characters below '0'.
ASSERT_FALSE(Demangle("_ZUtn3_", tmp, sizeof(tmp)));
ASSERT_FALSE(Demangle("_ZUlvEn3_", tmp, sizeof(tmp)));

// ParseNumber truncates to int, so an in-range-looking <number> can also
// arrive negative.
ASSERT_FALSE(Demangle("_ZUt2147483648_", tmp, sizeof(tmp)));
ASSERT_FALSE(Demangle("_ZUlvE2147483648_", tmp, sizeof(tmp)));

// The largest <number> whose index still fits in an int is unaffected.
ASSERT_TRUE(Demangle("_ZUt2147483645_", tmp, sizeof(tmp)));
EXPECT_STREQ(tmp, "{unnamed type#2147483647}");
}

TEST(Demangle, SubstpackNotationForTroublesomeTemplatePack) {
char tmp[100];

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