Git Has a Variable Named false_but_the_compiler_does_not_know_it
The article discusses a peculiar variable in Git's source code named 'false_but_the_compiler_does_not_know_it_'. This variable is used in a macro to prevent the compiler from optimizing out certain code, which could lead to false positives during compilation. The trick allows Git to maintain code functionality while avoiding compiler warnings about unreachable code.
- ▪The variable 'false_but_the_compiler_does_not_know_it_' is initialized to 0 and never modified in Git's codebase.
- ▪It is used in a macro called NOT_CONSTANT to prevent compiler optimizations that could trigger warnings.
- ▪This approach allows Git to handle specific code scenarios without raising unnecessary compiler errors.
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Why Git Has a Variable Named false_but_the_compiler_does_not_know_itA small C trick that keeps Clang from flagging valid code as unreachableAbhinav UpadhyayJun 03, 2026ShareToday, in weird C code tricks, I want to show you a small example from Git’s source code.Recently, I was poking around the Git source when a directory name caught my eye, it was named “compiler-tricks”. I thought, “This is a promising name, let’s see what’s inside of it”.Inside this directory, there was a file called not-constant.c, and the whole file contained just this:#include <git-compat-util.h> int false_but_the_compiler_does_not_know_it_ = 0;The variable name made me curious.
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