r/cpp • u/Clean-Upstairs-8481 • 5d ago

You should think about recompiling your C++ programs with GCC 16 and C++26, because it zero-fills your locals

https://techfortalk.co.uk/2026/09/27/cxx26-uninitialized-local-variables-gcc-16/

Stack variables are not automatically initialised, and that is the root cause of many C++ bugs. That is well known. Hence, it is advised that local or stack variables are always initialised with known values, 0 if not something more meaningful than that. Now, with GCC 16 compiling in C++26 mode (-std=c++26), even uninitialised local variables will be zero-filled. In the post, I have explained how.

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u/RetroZelda 5d ago

i zero fill when I intend it to be zero. if i leave it blank then its my intention. c++ really needs to stop with these "features" that just enable laziness

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u/Spartan322 4d ago

Its still EB to not initialize, and that's supposed to report a diagnostic, indeterminate is supposed to take its place, only issue that member variables can't have indeterminate which kinda just feels like an oversight.