[libcxxabi] r238263 - Make sure !empty() before calling String::front().

[Chaoren Lin]

Hi David,

Thanks for your concern.

The commit was intentional. I was hoping this small commit would fall under
this part:

smaller changes can be reviewed after commit


of the LLVM Developer Policy
<http://llvm.org/docs/DeveloperPolicy.html#code-reviews>

We inlined a copy of this file in LLDB for Windows, and I ran into a
problem where any mangled names with pointers or references in their
argument list would cause a crash. Turns out that on Linux, String::front()
consistently returns '\0' when empty, even though it should be undefined
behavior.

It should be covered by existing tests if you enable asserts for libcxx and
try to demangle "_Z1FPiRiOiMS0_FiiE".

Thanks,
Chaoren

On Tue, May 26, 2015 at 4:43 PM, David Majnemer <david.majnemer at gmail.com>
wrote:

> I didn't see anyone LGTM the phabricator review and no test has been added
> for this change.  Perhaps you accidentally committed this?
>
> On Tue, May 26, 2015 at 4:14 PM, Chaoren Lin <chaorenl at google.com> wrote:
>
>> Author: chaoren
>> Date: Tue May 26 18:14:26 2015
>> New Revision: 238263
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=238263&view=rev
>> Log:
>> Make sure !empty() before calling String::front().
>>
>> Reviewers: howard.hinnant
>>
>> Subscribers: cfe-commits
>>
>> Differential Revision: http://reviews.llvm.org/D9954
>>
>> Modified:
>>     libcxxabi/trunk/src/cxa_demangle.cpp
>>
>> Modified: libcxxabi/trunk/src/cxa_demangle.cpp
>> URL:
>> http://llvm.org/viewvc/llvm-project/libcxxabi/trunk/src/cxa_demangle.cpp?rev=238263&r1=238262&r2=238263&view=diff
>>
>> ==============================================================================
>> --- libcxxabi/trunk/src/cxa_demangle.cpp (original)
>> +++ libcxxabi/trunk/src/cxa_demangle.cpp Tue May 26 18:14:26 2015
>> @@ -1671,7 +1671,7 @@ parse_pointer_to_member_type(const char*
>>                  auto func = std::move(db.names.back());
>>                  db.names.pop_back();
>>                  auto class_type = std::move(db.names.back());
>> -                if (func.second.front() == '(')
>> +                if (!func.second.empty() && func.second.front() == '(')
>>                  {
>>                      db.names.back().first = std::move(func.first) + "("
>> + class_type.move_full() + "::*";
>>                      db.names.back().second = ")" +
>> std::move(func.second);
>> @@ -2018,7 +2018,8 @@ parse_type(const char* first, const char
>>                                      db.names[k].first += " (";
>>                                      db.names[k].second.insert(0, ")");
>>                                  }
>> -                                else if (db.names[k].second.front() ==
>> '(')
>> +                                else if (!db.names[k].second.empty() &&
>> +                                          db.names[k].second.front() ==
>> '(')
>>                                  {
>>                                      db.names[k].first += "(";
>>                                      db.names[k].second.insert(0, ")");
>> @@ -2045,7 +2046,8 @@ parse_type(const char* first, const char
>>                                      db.names[k].first += " (";
>>                                      db.names[k].second.insert(0, ")");
>>                                  }
>> -                                else if (db.names[k].second.front() ==
>> '(')
>> +                                else if (!db.names[k].second.empty() &&
>> +                                          db.names[k].second.front() ==
>> '(')
>>                                  {
>>                                      db.names[k].first += "(";
>>                                      db.names[k].second.insert(0, ")");
>> @@ -2079,7 +2081,8 @@ parse_type(const char* first, const char
>>                                      db.names[k].first += " (";
>>                                      db.names[k].second.insert(0, ")");
>>                                  }
>> -                                else if (db.names[k].second.front() ==
>> '(')
>> +                                else if (!db.names[k].second.empty() &&
>> +                                          db.names[k].second.front() ==
>> '(')
>>                                  {
>>                                      db.names[k].first += "(";
>>                                      db.names[k].second.insert(0, ")");
>>
>>
>> _______________________________________________
>> cfe-commits mailing list
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>>
>
>
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