Fix Makefile handling of user CXXFLAGS & also add a DEBUG flag #990
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The way `CXXFLAGS` and other flags were being set meant that users had to add the default values (`-std=c++17 -fopenmp -O3` etc) if they set the flags at all. The new approach here adds the user values to the existing ones, so that they can override values more selectively. This also adds a DEBUG flag that switches between using `-g -O0` and the regular `-O3` option.
Clang doesn't understand `-flto=auto` and G++ doesn't understand `-flto`.
sergeisakov
approved these changes
Jan 6, 2026
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The way
CXXFLAGSand other flags were being set meant that users had to add the default values (-std=c++17 -fopenmp -O3etc) if they set the flags at all, or else lose the defaults. This was error-prone and suboptimal. The change here makes it so that the user values are appended at the end of the defaults, so that they can override values.This PR also adds a DEBUG flag that switches between using
-g -O0and the regular-O3option. Developers can invoke it using, e.g.,make DEBUG=1.