On Nov 7, 2007, David Edelsohn <[EMAIL PROTECTED]> wrote: > Who is "we"? What better debugging are GCC users demanding? What > debugging difficulties are they experiencing?
I, for one, miss the arguments of inlined functions, a lot. The reason for that is that arguments are currently optimized away to boot. Even if they weren't, since they're initialized with a trivial copy, at least their initial value (quite often preserved throughout compilation) would be gone to boot. On top of that, we currently regard arguments and variables of non-inlined functions as special, and we prevent a number of optimizations with them, in order to be able to generate slightly better debug information for them. (As for arguments and variables of inlined functions, we happily drop them on the floor right away.) This is not only inconsistent, it's also harmful, because we're trading performance and compile-time memory for slightly better but still incorrect, incomplete and unreliable debug information. > Who is that set of users? I'm personally getting numerous requests for debug information correctness and better completeness from debug info consumers such as gdb, frysk and systemtap. GCC's eagerness to inline functions, even ones never declared as inline, and its eagerness to corrupt the meta-information associated with them, causes these tools to malfunction in very many situations. And it's all GCC's fault, for generating code that is not standards-compliant in the meta-information sections of its output. > What functional changes would improve those cases? What is the cost of > those improvements in complexity, maintainability, compile time, object > file size, GDB start-up time, etc.? Before I spend hours describing the little I can foresee about this, how much of this really matters, given that it's mostly a matter of correctness, rather than mere trade offs? -- Alexandre Oliva http://www.lsd.ic.unicamp.br/~oliva/ FSF Latin America Board Member http://www.fsfla.org/ Red Hat Compiler Engineer [EMAIL PROTECTED], gcc.gnu.org} Free Software Evangelist [EMAIL PROTECTED], gnu.org}
