------- Comment #7 from wilson at specifix dot com 2005-12-06 03:03 ------- Subject: Re: New: [2.95.2/3.3.3/4.0.0 Regression] g++ fails to emit debug information for SOME local variables in class member function that has templated local variables
schaudhu at blackrock dot com wrote: > When trying to debug the following block of code, some of the function's local > variables can not be displayed using display, print, or info scope > [function]. > Display and print will work after a certain point within the stack frame of > the > function foo(), but long after the variables are initialized. Please examine > the following source code and output. Part of the problem here is understanding what "scope" means. The gdb command "info scope foo" will only print variables in the outer-most function scope for foo, i.e. variables whose scope starts at the beginning of the function. In your testcase, mfact is defined part-way into the function. Older gcc versions probably lie, and say that mfact has the same scope as foo. Newer gcc versions try to emit accurate scope info, creating a lexical block to represent where mfact is live, even though there is no lexical block in the input. So with gcc-4.x, info scope foo does not report mfact, and this is correct, because mfact is defined in a subscope. If you try something like "info scope test.cc:37" then you will get all symbols you are expecting to see, as they are all live at this point. So there is no gcc problem here, though one could perhaps argue that the gdb info scope command output is confusing and needs to be improved. With gcc-3.3, things are a bit more confused. The scope info changes depending on whether -DGOODDGB is defined, which seems wrong. With it defined, rcode/n/mfacts all have function wide scope. Without it defined, only mfacts has function scope. The others, rcode/n/nfacts are all defined in a subscope. I didn't look at why this happens. This does appear to be a bug. Oh, by the way, your g++ -DGOODDBG example is wrong. You claim that a symbol is missing, but that symbol is excluded when -DGOODDBG is defined, so there is no problem there. I tried gcc-3.4, and the scope info looks OK, i.e. roughly the same as gcc-4.0. Based on the info you have provided, and the fact that we are no longer maintaining gcc-3.3, I don't see anything here to fix. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25234
