[flang-commits] [flang] [flang][docs] Add a mention about -fsafe-trampoline to FAQ.md (PR #207656)

[Sairudra More via flang-commits]

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@@ -50,3 +50,7 @@ ld.lld: error: src.o: requires an executable stack, but -z execstack is not spec
 flang-22: error: linker command failed with exit code 1 (use -v to see invocation)
 $ flang src.f90 -fuse-ld=lld -Wl,-z,execstack
 ```
+
+Since LLVM 23, Flang has a new compiler flag `-fsafe-trampoline`, which is disabled by default.
+If this is enabled, the trampoline is generated on a dedicated `mmap`'d region instead of the stack.
+Therefore, we **strongly recommend** using this flag to reduce the security risk.
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Saieiei wrote:

Could we qualify this recommendation with the supported targets?

`-fsafe-trampoline` is only forwarded by the driver for x86-64 and AArch64 targets; on other targets it warns and is not passed to `-fc1`. So maybe:

`Since LLVM 23, Flang has a new compiler flag -fsafe-trampoline, which is disabled by default and is currently supported on x86-64 and AArch64 targets. Where supported, we recommend using this flag to reduce the security risk.`


https://github.com/llvm/llvm-project/pull/207656