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lua: avoid gcc -Wreturn-local-addr bug 

Avoid a bug with gcc's -Wreturn-local-addr warning with some
obfuscation.  In buggy versions of gcc, if a return value is an
expression that involves the address of a local variable, and even if
that address is legally converted to a non-pointer type, a warning may
be emitted and the value of the address may be replaced with zero.
Howerver, buggy versions don't emit the warning or replace the value
when simply returning a local variable of non-pointer type.

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90737

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Ryan Libby <rlibby@FreeBSD.org>
Closes #11337
This commit is contained in:
Ryan Libby 2020-12-15 09:20:48 -08:00 committed by Brian Behlendorf
parent 1fbda9caee
commit ee49d9e02b
1 changed files with 6 additions and 4 deletions
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10
module/lua/ldo.c
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@ -33,14 +33,16 @@
#if defined (_KERNEL) && defined(__linux__) #if defined (_KERNEL) && defined(__linux__)
#include <asm/current.h> #include <asm/current.h>
static intptr_t stack_remaining(void) { static intptr_t stack_remaining(void) {
char local; intptr_t local;
return (intptr_t)(&local - (char *)current->stack); local = (intptr_t)&local - (intptr_t)current->stack;
return local;
} }
#elif defined (_KERNEL) && defined(__FreeBSD__) #elif defined (_KERNEL) && defined(__FreeBSD__)
#include <sys/pcpu.h> #include <sys/pcpu.h>
static intptr_t stack_remaining(void) { static intptr_t stack_remaining(void) {
char local; intptr_t local;
return (intptr_t)(&local - (char *)curthread->td_kstack); local = (intptr_t)&local - (intptr_t)curthread->td_kstack;
return local;
} }
#else #else
static intptr_t stack_remaining(void) { static intptr_t stack_remaining(void) {