GCC 3.0 Caveats

• -fstrict-aliasing is now part of -O2 and higher optimization levels. This allows the compiler to assume the strictest aliasing rules applicable to the language being compiled. For C and C++, this activates optimizations based on the type of expressions. This optimization may thus break old, non-compliant code.
• Enumerations are now properly promoted to int in function parameters and function returns. Normally this change is not visible, but when using -fshort-enums this is an ABI change.
• The undocumented extension that allowed C programs to have a label at the end of a compound statement has been deprecated and may be removed in a future version. Programs that now generate a warning about this may be fixed by adding a null statement (a single semicolon) after the label.
• The poorly documented extension that allowed string constants in C, C++ and Objective C to contain unescaped newlines has been deprecated and may be removed in a future version. Programs using this extension may be fixed in several ways: the bare newline may be replaced by \n, or preceded by \n\, or string concatenation may be used with the bare newline preceded by \n" and " placed at the start of the next line.
• The Chill compiler is not included in GCC 3.0, because of the lack of a volunteer to convert it to use garbage collection.
• Certain non-standard iostream methods from earlier versions of libstdc++ are not included in libstdc++ v3, i.e. filebuf::attach, ostream::form, and istream::gets. Here are workaround hints for: ostream::form, filebuf::attach.
• The new C++ ABI is not yet fully supported by current (as of 2001-07-01) releases and development versions of GDB, or any earlier versions. There is a problem setting breakpoints by line number, and other related issues that have been fixed in GCC 3.0 but not yet handled in GDB: http://gcc.gnu.org/ml/gcc-bugs/2001-06/msg00421.html

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Last modified 2006-06-21