https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109895
Bug ID: 109895 Summary: -Walloc-size-larger-than complains about code it generated itself under -flto -fno-exceptions Product: gcc Version: 13.1.1 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c++ Assignee: unassigned at gcc dot gnu.org Reporter: thiago at kde dot org Target Milestone: --- Reference: https://bugreports.qt.io/browse/QTBUG-113603 Code in question: const auto paramCount = mysql_stmt_param_count(d->stmt); if (paramCount > 0) // allocate memory for outvalues d->outBinds = new MYSQL_BIND[paramCount](); mysql_stmt_param_count returns unsigned long. GCC 13.1 with -flto -fno-exceptions produced: src/plugins/sqldrivers/mysql/qsql_mysql.cpp: In member function ‘prepare’: src/plugins/sqldrivers/mysql/qsql_mysql.cpp:891:50: warning: argument 1 value ‘18446744073709551615’ exceeds maximum object size 9223372036854775807 [-Walloc-size-larger-than=] 891 | d->outBinds = new MYSQL_BIND[paramCount](); | ^ /usr/include/c++/13/new:128:26: note: in a call to allocation function ‘operator new []’ declared here 128 | _GLIBCXX_NODISCARD void* operator new[](std::size_t) _GLIBCXX_THROW (std::bad_alloc) | ^ Disassembling the code shows it looks similar to this: https://godbolt.org/z/9eKPxbEMY movq $-1, %rdi cmpq %rbx, %rax jb .L2 ... .L2: call operator new[](unsigned long)@PLT So that 18446744073709551615 value is the -1 inserted by GCC itself to deal with the multiplication overflow.