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Suppress warning about stack_base_ptr with late-model GCC.

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GCC 12 complains that set_stack_base is storing the address of
a local variable in a long-lived pointer.  This is an entirely
reasonable warning (indeed, it just helped us find a bug);
but that behavior is intentional here.  We can work around it
by using __builtin_frame_address(0) instead of a specific local
variable; that produces an address a dozen or so bytes different,
in my testing, but we don't care about such a small difference.
Maybe someday a compiler lacking that function will start to issue
a similar warning, but we'll worry about that when it happens.

Patch by me, per a suggestion from Andres Freund.  Back-patch to
v12, which is as far back as the patch will go without some pain.
(Recently-established project policy would permit a back-patch as
far as 9.2, but I'm disinclined to expend the work until GCC 12
is much more widespread.)

Discussion: https://postgr.es/m/3773792.1645141467@sss.pgh.pa.us
This commit is contained in:
Tom Lane
2022-02-17 22:45:34 -05:00
parent a9e186da81
commit 2e30d77a19
8 changed files with 86 additions and 8 deletions
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3
configure.ac
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@ -1769,6 +1769,9 @@ PGAC_CHECK_BUILTIN_FUNC([__builtin_bswap64], [long int x])
PGAC_CHECK_BUILTIN_FUNC([__builtin_clz], [unsigned int x])
PGAC_CHECK_BUILTIN_FUNC([__builtin_ctz], [unsigned int x])
PGAC_CHECK_BUILTIN_FUNC([__builtin_popcount], [unsigned int x])
# __builtin_frame_address may draw a diagnostic for non-constant argument,
# so it needs a different test function.
PGAC_CHECK_BUILTIN_FUNC_PTR([__builtin_frame_address], [0])
# We require 64-bit fseeko() to be available, but run this check anyway
# in case it finds that _LARGEFILE_SOURCE has to be #define'd for that.