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Commitc04d35f

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Try to detect runtime unavailability of __builtin_mul_overflow(int64).
On some systems the results of 64 bit __builtin_mul_overflow()operations can be computed at compile time, but not at runtime. Theknown cases are arm buildfar animals using clang where the runtimeoperation is implemented in a unavailable function.Try to avoid compile-time computation by using volatile arguments to__builtin_mul_overflow(). In that case we hopefully will get a linkerror when unavailable, similar to what buildfarm animals dangomushiand gull are reporting.Author: Andres FreundDiscussion:https://postgr.es/m/20171213213754.pydkyjs6bt2hvsdb@alap3.anarazel.de
1 parentc757a3d commitc04d35f

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‎config/c-compiler.m4‎

Lines changed: 8 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -310,13 +310,17 @@ fi])# PGAC_C_BUILTIN_CONSTANT_P
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# and define HAVE__BUILTIN_OP_OVERFLOW if so.
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#
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# Check for the most complicated case, 64 bit multiplication, as a
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# proxy for all of the operations. Have to link to be sure to
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# recognize a missing __builtin_mul_overflow.
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# proxy for all of the operations. Use volatile variables to avoid the
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# compiler computing result at compile time, even though the runtime
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# might not supply operation. Have to link to be sure to recognize a
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# missing __builtin_mul_overflow.
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AC_DEFUN([PGAC_C_BUILTIN_OP_OVERFLOW],
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[AC_CACHE_CHECK(for__builtin_mul_overflow,pgac_cv__builtin_op_overflow,
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[AC_LINK_IFELSE([AC_LANG_PROGRAM([],
318-
[PG_INT64_TYPE result;
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__builtin_mul_overflow((PG_INT64_TYPE) 1, (PG_INT64_TYPE) 2, &result);]
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[PG_INT64_TYPE a = 1;
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PG_INT64_TYPE b = 1;
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PG_INT64_TYPE result;
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__builtin_mul_overflow(*(volatile PG_INT64_TYPE *) a, *(volatile PG_INT64_TYPE *) b, &result);]
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)],
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[pgac_cv__builtin_op_overflow=yes],
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[pgac_cv__builtin_op_overflow=no])])

‎configure‎

Lines changed: 3 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -14488,8 +14488,10 @@ else
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int
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main ()
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{
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PG_INT64_TYPE a = 1;
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PG_INT64_TYPE b = 1;
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PG_INT64_TYPE result;
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__builtin_mul_overflow((PG_INT64_TYPE) 1, (PG_INT64_TYPE) 2, &result);
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__builtin_mul_overflow(*(volatilePG_INT64_TYPE *) a, *(volatilePG_INT64_TYPE *) b, &result);
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;
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return 0;

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