1*8975f5c5SAndroid Build Coastguard Worker // Copyright 2023 The Chromium Authors 2*8975f5c5SAndroid Build Coastguard Worker // Use of this source code is governed by a BSD-style license that can be 3*8975f5c5SAndroid Build Coastguard Worker // found in the LICENSE file. 4*8975f5c5SAndroid Build Coastguard Worker 5*8975f5c5SAndroid Build Coastguard Worker // This file has been copied from //base/debug/alias.h (and then trimmed to just 6*8975f5c5SAndroid Build Coastguard Worker // the APIs / macros needed by //build/rust/std; additionally the APIs were 7*8975f5c5SAndroid Build Coastguard Worker // moved into the `build_rust_std` namespace). 8*8975f5c5SAndroid Build Coastguard Worker // 9*8975f5c5SAndroid Build Coastguard Worker // TODO(crbug.com/40279749): Avoid code duplication / reuse code. 10*8975f5c5SAndroid Build Coastguard Worker 11*8975f5c5SAndroid Build Coastguard Worker #ifndef BUILD_RUST_STD_ALIAS_H_ 12*8975f5c5SAndroid Build Coastguard Worker #define BUILD_RUST_STD_ALIAS_H_ 13*8975f5c5SAndroid Build Coastguard Worker 14*8975f5c5SAndroid Build Coastguard Worker #include <stddef.h> 15*8975f5c5SAndroid Build Coastguard Worker 16*8975f5c5SAndroid Build Coastguard Worker namespace build_rust_std { 17*8975f5c5SAndroid Build Coastguard Worker namespace debug { 18*8975f5c5SAndroid Build Coastguard Worker 19*8975f5c5SAndroid Build Coastguard Worker // Make the optimizer think that |var| is aliased. This can be used to prevent a 20*8975f5c5SAndroid Build Coastguard Worker // local variable from being optimized out (which is something that 21*8975f5c5SAndroid Build Coastguard Worker // `NO_CODE_FOLDING` macro definition below depends on). See 22*8975f5c5SAndroid Build Coastguard Worker // //base/debug/alias.h for more details. 23*8975f5c5SAndroid Build Coastguard Worker void Alias(const void* var); 24*8975f5c5SAndroid Build Coastguard Worker 25*8975f5c5SAndroid Build Coastguard Worker } // namespace debug 26*8975f5c5SAndroid Build Coastguard Worker 27*8975f5c5SAndroid Build Coastguard Worker } // namespace build_rust_std 28*8975f5c5SAndroid Build Coastguard Worker 29*8975f5c5SAndroid Build Coastguard Worker // Prevent code folding (where a linker identifies functions that are 30*8975f5c5SAndroid Build Coastguard Worker // bit-identical and overlays them, which saves space but it leads to confusing 31*8975f5c5SAndroid Build Coastguard Worker // call stacks because multiple symbols are at the same address). See 32*8975f5c5SAndroid Build Coastguard Worker // //base/debug/alias.h for more details. 33*8975f5c5SAndroid Build Coastguard Worker #define NO_CODE_FOLDING() \ 34*8975f5c5SAndroid Build Coastguard Worker const int line_number = __LINE__; \ 35*8975f5c5SAndroid Build Coastguard Worker build_rust_std::debug::Alias(&line_number) 36*8975f5c5SAndroid Build Coastguard Worker 37*8975f5c5SAndroid Build Coastguard Worker #endif // BUILD_RUST_STD_ALIAS_H_ 38