+2020-05-23 Paul Eggert <eggert@cs.ucla.edu>
+
+ verify: document ‘assume’ better
+ * lib/verify.h (assume): Say it’s for static analysis, not dynamic.
+
2020-05-22 Asher Gordon <AsDaGo@posteo.net>
gendocs: Clarify licenses for templates.
#endif
/* Assume that R always holds. Behavior is undefined if R is false,
- fails to evaluate, or has side effects. Although assuming R can
- help a compiler generate better code or diagnostics, performance
- can suffer if R uses hard-to-optimize features such as function
- calls not inlined by the compiler. */
+ fails to evaluate, or has side effects.
+
+ 'assume (R)' is a directive from the programmer telling the
+ compiler that R is true so the compiler needn't generate code to
+ test R. This is why 'assume' is in verify.h: it's related to
+ static checking (in this case, static checking done by the
+ programmer), not dynamic checking.
+
+ 'assume (R)' can affect compilation of all the code, not just code
+ that happens to be executed after the assume (R) is "executed".
+ For example, if the code mistakenly does 'assert (R); assume (R);'
+ the compiler is entitled to optimize away the 'assert (R)'.
+
+ Although assuming R can help a compiler generate better code or
+ diagnostics, performance can suffer if R uses hard-to-optimize
+ features such as function calls not inlined by the compiler. */
#if _GL_HAS_BUILTIN_UNREACHABLE
# define assume(R) ((R) ? (void) 0 : __builtin_unreachable ())