Re: [PATCH] libstdc++: fix allocate_at_least test for small alignments [PR126072]

Jonathan Wakely Fri, 03 Jul 2026 07:41:02 -0700

On Wed, 01 Jul 2026 at 21:08 -0400, Nathan Myers wrote:

A test for P0401 allocate_at_least fails on target cris-elf,
which has a default allocator with alignment 4. This patch
adjusts tests to accommodate alignments down to 1, and removes
assumptions about the size of short int.


Tested on x86 -m64 and -m32. Need assistance for cris-elf.

OK

libstdc++-v3/Changelog:
        PR libstdc++/126072
        * testsuite/20_util/allocator/allocate_at_least.cc
---
.../20_util/allocator/allocate_at_least.cc    | 181 ++++++++++--------
1 file changed, 100 insertions(+), 81 deletions(-)

diff --git a/libstdc++-v3/testsuite/20_util/allocator/allocate_at_least.cc 
b/libstdc++-v3/testsuite/20_util/allocator/allocate_at_least.cc
index 987e2472490..0dcfcefc2c9 100644
--- a/libstdc++-v3/testsuite/20_util/allocator/allocate_at_least.cc
+++ b/libstdc++-v3/testsuite/20_util/allocator/allocate_at_least.cc
@@ -73,17 +73,19 @@ void extra()
    VERIFY(n == __STDCPP_DEFAULT_NEW_ALIGNMENT__);
    SatC::deallocate(satc, p, n);
  }
-  {
-    auto [p, n] = SatC::allocate_at_least(satc, 2);
-    VERIFY(n == __STDCPP_DEFAULT_NEW_ALIGNMENT__);
-    SatC::deallocate(satc, p, n);
-  }
-  {
-    auto [p, n] =
-      SatC::allocate_at_least(satc, __STDCPP_DEFAULT_NEW_ALIGNMENT__ - 1);
-    VERIFY(n == __STDCPP_DEFAULT_NEW_ALIGNMENT__);
-    SatC::deallocate(satc, p, n);
-  }
+  if constexpr (__STDCPP_DEFAULT_NEW_ALIGNMENT__ >= 2)
+    {
+      auto [p, n] = SatC::allocate_at_least(satc, 2);
+      VERIFY(n == __STDCPP_DEFAULT_NEW_ALIGNMENT__);
+      SatC::deallocate(satc, p, n);
+    }
+  if constexpr (__STDCPP_DEFAULT_NEW_ALIGNMENT__ > 1)
+    {
+      auto [p, n] =
+       SatC::allocate_at_least(satc, __STDCPP_DEFAULT_NEW_ALIGNMENT__ - 1);
+      VERIFY(n == __STDCPP_DEFAULT_NEW_ALIGNMENT__);
+      SatC::deallocate(satc, p, n);
+    }
  {
    auto [p, n] = SatC::allocate_at_least(
        satc, __STDCPP_DEFAULT_NEW_ALIGNMENT__);
@@ -91,77 +93,94 @@ void extra()
    SatC::deallocate(satc, p, n);
  }

-  using SatS = std::allocator_traits<std::allocator<short>>;
-  std::allocator<short> sats;
-  {
-    auto [p, n] = SatS::allocate_at_least(sats, 1);
-    VERIFY(n == __STDCPP_DEFAULT_NEW_ALIGNMENT__ / sizeof(short));
-    SatS::deallocate(sats, p, n);
-  }
-  {
-    auto [p, n] = SatS::allocate_at_least(sats, 2);
-    VERIFY(n == __STDCPP_DEFAULT_NEW_ALIGNMENT__ / sizeof(short));
-    SatS::deallocate(sats, p, n);
-  }
-  {
-    auto [p, n] = SatS::allocate_at_least(sats,
-       (__STDCPP_DEFAULT_NEW_ALIGNMENT__ - 1) / sizeof(short));
-    VERIFY(n == __STDCPP_DEFAULT_NEW_ALIGNMENT__ / sizeof(short));
-    SatS::deallocate(sats, p, n);
-  }
-  {
-    auto [p, n] = SatS::allocate_at_least(sats,
-       __STDCPP_DEFAULT_NEW_ALIGNMENT__ / sizeof(short));
-    VERIFY(n == __STDCPP_DEFAULT_NEW_ALIGNMENT__ / sizeof(short));
-    SatS::deallocate(sats, p, n);
-  }
-
-  struct A3 { char s[3]; };
-  using SatA3 = std::allocator_traits<std::allocator<A3>>;
-  std::allocator<A3> sata3;
-  {
-    auto [p, n] = SatA3::allocate_at_least(sata3, 1);
-    VERIFY(n == __STDCPP_DEFAULT_NEW_ALIGNMENT__ / sizeof(A3));
-    SatA3::deallocate(sata3, p, n);
-  }
-  {
-    auto [p, n] = SatA3::allocate_at_least(sata3, 2);
-    VERIFY(n == __STDCPP_DEFAULT_NEW_ALIGNMENT__ / sizeof(A3));
-    SatA3::deallocate(sata3, p, n);
-  }
-  {
-    auto [p, n] = SatA3::allocate_at_least(sata3,
-       (__STDCPP_DEFAULT_NEW_ALIGNMENT__ - 1) / sizeof(A3));
-    VERIFY(n == __STDCPP_DEFAULT_NEW_ALIGNMENT__ / sizeof(A3));
-    SatA3::deallocate(sata3, p, n);
-  }
-  {
-    auto [p, n] = SatA3::allocate_at_least(sata3,
-       __STDCPP_DEFAULT_NEW_ALIGNMENT__ / sizeof(A3));
-    VERIFY(n == __STDCPP_DEFAULT_NEW_ALIGNMENT__ / sizeof(A3));
-    SatA3::deallocate(sata3, p, n);
-  }
+  if constexpr (__STDCPP_DEFAULT_NEW_ALIGNMENT__ > 2)
+    {
+      struct A2 { char s[2]; };
+      using SatA2 = std::allocator_traits<std::allocator<A2>>;
+      std::allocator<A2> sats;
+      if (sizeof(A2) <= __STDCPP_DEFAULT_NEW_ALIGNMENT__)
+      {
+       auto [p, n] = SatA2::allocate_at_least(sats, 1);
+       VERIFY(n == __STDCPP_DEFAULT_NEW_ALIGNMENT__ / sizeof(A2));
+       SatA2::deallocate(sats, p, n);
+      }
+      if (2*sizeof(A2) < __STDCPP_DEFAULT_NEW_ALIGNMENT__)
+      {
+       auto [p, n] = SatA2::allocate_at_least(sats, 2);
+       VERIFY(n == __STDCPP_DEFAULT_NEW_ALIGNMENT__ / sizeof(A2));
+       SatA2::deallocate(sats, p, n);
+      }
+      if ((__STDCPP_DEFAULT_NEW_ALIGNMENT__ - 1) / sizeof(A2) > 0)
+      {
+       auto [p, n] = SatA2::allocate_at_least(sats,
+           (__STDCPP_DEFAULT_NEW_ALIGNMENT__ - 1) / sizeof(A2));
+       VERIFY(n == __STDCPP_DEFAULT_NEW_ALIGNMENT__ / sizeof(A2));
+       SatA2::deallocate(sats, p, n);
+      }
+      if (__STDCPP_DEFAULT_NEW_ALIGNMENT__ / sizeof(A2) > 0)
+      {
+       auto [p, n] = SatA2::allocate_at_least(sats,
+           __STDCPP_DEFAULT_NEW_ALIGNMENT__ / sizeof(A2));
+       VERIFY(n == __STDCPP_DEFAULT_NEW_ALIGNMENT__ / sizeof(A2));
+       SatA2::deallocate(sats, p, n);
+      }
+    }

-  struct Anm1 { char s[__STDCPP_DEFAULT_NEW_ALIGNMENT__ - 1]; };
-  using SatAnm1 = std::allocator_traits<std::allocator<Anm1>>;
-  std::allocator<Anm1> satanm1;
-  {
-    auto [p, n] = SatAnm1::allocate_at_least(satanm1, 1);
-    VERIFY(n == 1);
-    SatAnm1::deallocate(satanm1, p, n);
-  }
-  {
-    auto [p, n] = SatAnm1::allocate_at_least(satanm1,
-       __STDCPP_DEFAULT_NEW_ALIGNMENT__);
-    VERIFY(n == __STDCPP_DEFAULT_NEW_ALIGNMENT__);
-    SatAnm1::deallocate(satanm1, p, n);
-  }
-  {
-    auto [p, n] = SatAnm1::allocate_at_least(satanm1,
-       __STDCPP_DEFAULT_NEW_ALIGNMENT__ - 1);
-    VERIFY(n == __STDCPP_DEFAULT_NEW_ALIGNMENT__);
-    SatAnm1::deallocate(satanm1, p, n);
-  }
+  if constexpr (__STDCPP_DEFAULT_NEW_ALIGNMENT__ > 2)
+    {
+      struct A3 { char s[3]; };
+      using SatA3 = std::allocator_traits<std::allocator<A3>>;
+      std::allocator<A3> sata3;
+      {
+       auto [p, n] = SatA3::allocate_at_least(sata3, 1);
+       VERIFY(n == __STDCPP_DEFAULT_NEW_ALIGNMENT__ / sizeof(A3));
+       SatA3::deallocate(sata3, p, n);
+      }
+      if constexpr (2*sizeof(A3) <= __STDCPP_DEFAULT_NEW_ALIGNMENT__)
+       {
+         auto [p, n] = SatA3::allocate_at_least(sata3, 2);
+         VERIFY(n == __STDCPP_DEFAULT_NEW_ALIGNMENT__ / sizeof(A3));
+         SatA3::deallocate(sata3, p, n);
+       }
+      if constexpr ((__STDCPP_DEFAULT_NEW_ALIGNMENT__ - 1) / sizeof(A3) > 0)
+       {
+         auto [p, n] = SatA3::allocate_at_least(sata3,
+             (__STDCPP_DEFAULT_NEW_ALIGNMENT__ - 1) / sizeof(A3));
+         VERIFY(n == __STDCPP_DEFAULT_NEW_ALIGNMENT__ / sizeof(A3));
+         SatA3::deallocate(sata3, p, n);
+       }
+      if constexpr (__STDCPP_DEFAULT_NEW_ALIGNMENT__ / sizeof(A3) > 0)
+       {
+         auto [p, n] = SatA3::allocate_at_least(sata3,
+             __STDCPP_DEFAULT_NEW_ALIGNMENT__ / sizeof(A3));
+         VERIFY(n == __STDCPP_DEFAULT_NEW_ALIGNMENT__ / sizeof(A3));
+         SatA3::deallocate(sata3, p, n);
+       }
+    }
+
+  if constexpr (__STDCPP_DEFAULT_NEW_ALIGNMENT__ > 1)
+    {
+      struct Anm1 { char s[__STDCPP_DEFAULT_NEW_ALIGNMENT__ - 1]; };
+      using SatAnm1 = std::allocator_traits<std::allocator<Anm1>>;
+      std::allocator<Anm1> satanm1;
+      {
+       auto [p, n] = SatAnm1::allocate_at_least(satanm1, 1);
+       VERIFY(n == 1);
+       SatAnm1::deallocate(satanm1, p, n);
+      }
+      {
+       auto [p, n] = SatAnm1::allocate_at_least(satanm1,
+           __STDCPP_DEFAULT_NEW_ALIGNMENT__);
+       VERIFY(n == __STDCPP_DEFAULT_NEW_ALIGNMENT__);
+       SatAnm1::deallocate(satanm1, p, n);
+      }
+      {
+       auto [p, n] = SatAnm1::allocate_at_least(satanm1,
+           __STDCPP_DEFAULT_NEW_ALIGNMENT__ - 1);
+       VERIFY(n == __STDCPP_DEFAULT_NEW_ALIGNMENT__);
+       SatAnm1::deallocate(satanm1, p, n);
+      }
+    }
}

int main()
--
2.54.0

Re: [PATCH] libstdc++: fix allocate_at_least test for small alignments [PR126072]

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