GNU Arm Embedded Toolchain

erroneous "no return" warning on naked static function

Bug #1836547 reported by Ling LI
6
This bug affects 1 person
Affects Status Importance Assigned to Milestone
GNU Arm Embedded Toolchain
Fix Committed
Undecided
Richard Sandiford

Bug Description

To be clear, it happens only to static naked functions; externs are not affected. Test case:

gcc version 7.3.1 20180622 (release) [ARM/embedded-7-branch revision 261907] (GNU Tools for Arm Embedded Processors 7-2018-q2-update)

static int __attribute__((naked)) fn(int a, int b)
{
   asm("bx lr");
}

And the message reads:
warning: no return statement in function returning non-void [-Wreturn-type]

A fake C return statement removes this warning, but may add dead code. More importantly, armclang doesn't allow return in naked functions, extern or static; it treats it as an error.

It might worth fixing for reduced annoyance and better consistency between static/extern and also gcc-arm/armclang.

Revision history for this message
Ramana Radhakrishnan (ramana) wrote :

Again invalid, I don't see an easy route to fix this as the compiler cannot reason about code inside an inline assembler block.

Changed in gcc-arm-embedded:
status: New → Invalid
Revision history for this message
Richard Sandiford (rsandifo-arm) wrote :

The C++ compiler handles this correctly, but the C compiler doesn't.

Changed in gcc-arm-embedded:
status: Invalid → Confirmed
assignee: nobody → Richard Sandiford (rsandifo-arm)
status: Confirmed → In Progress
Revision history for this message
Richard Sandiford (rsandifo-arm) wrote :

Thanks for the report. This is now fixed in GCC 8 branch and later. The fix should be in the next release of the GNU Arm Embedded Toolchain.

Changed in gcc-arm-embedded:
status: In Progress → Fix Committed
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