Remove non-Standard TR1 #5763

StephanTLavavej · 2025-10-04T20:21:55Z

Overview

This permanently removes our non-Standard TR1 implementation, which was superseded by C++11.

Fixes #183. Fixes #1002. (And DevCom-381099 / Microsoft-internal VSO-729899.)

The std::tr1 namespace mostly consisted of aliases for Standard machinery. For example, std::tr1::shared_ptr was just an alias for std::shared_ptr. One member function was affected: in <array>, TR1 array::assign() was superseded by Standard array::fill(). The most significant differences were in <random>, where the old engines and distributions were superseded by ones with new names and superior interfaces. For example, TR1 mersenne_twister and uniform_int were superseded by Standard mersenne_twister_engine and uniform_int_distribution.

Eliminating TR1 removes unnecessary complexity from this fiendishly complex library. For users, it removes ways to write non-portable code. For library implementers, it reduces our maintenance burden, making it easier for us to reason about the remaining Standard code. We've been working towards TR1 removal for a long time:

In Aug 2017, VS 2017 15.3 shipped, removing most of TR1's machinery by default in C++17 mode and later.

In Dec 2017, VS 2017 15.5 shipped a warning to users that "The non-Standard std::tr1 namespace and TR1-only machinery are deprecated and will be REMOVED."

In May 2024, VS 2022 17.10 shipped #4284, which extended the deprecation warnings to the non-Standard TR1 engines and distributions in <random> that were also available in the std namespace because they served as base classes for the Standard engines and distributions.

Very recently, my #5712 disconnected the Standard engines and distributions from their TR1 ancestors, making it possible to finally remove TR1. And now, the conclusion.

In addition to removing the std::tr1 namespace, the old array member function, and the old engines and distributions lurking in the std namespace, this makes two more significant simplifications possible. Because the old engines had a different interface, various algorithms had to accept either old or new engines. We can now drop that logic, always using the more efficient new interface. Also, subtract_with_carry_engine had a complicated implementation, which was previously tangled up with somewhat different TR1 engines that had been abandoned during Standardization. Following up on #5712, I can fuse another base class, and a traits class, away. (This is the bulk of the commits and complexity in this PR.)

Commits

Require Standard URBGs, delete machinery for TR1 generators.
Remove _HAS_TR1_NAMESPACE.
Remove _SILENCE_TR1_NAMESPACE_DEPRECATION_WARNING.
Remove _SILENCE_TR1_RANDOM_DEPRECATION_WARNING.
Simplify test for removed non-Standard names.
Drop _Swc_base operator>>() and operator<<(), and _Swc_traits::_Write().
- They were unused by subtract_with_carry_engine.
Drop _Swc_base min() and max(), and _Swc_traits::_Max.
- They were unused by subtract_with_carry_engine.
Fuse _Swc_base operator()() with strengthened noexcept.
Fuse _Swc_base discard().
Fuse _Swc_base operator==().
- We don't need to static_cast when calling _Left._Equals(_Right).
Fuse _Swc_base default_seed.
Introduce and consistently use _Mytraits in _Swc_base and subtract_with_carry_engine to make fusion easier and avoid shadowing.
Fuse _Swc_base _Write_full().
Drop _Swc_base default ctor and ctor/seed() from _Gen&.
- They were unused.
Fuse _Swc_base construction.
- Avoid redundant seeding in subtract_with_carry_engine(_Seed_seq&).
Fuse _Swc_base seed().
- _Readcy was always false.
Finish fusing _Swc_base.
- Note that _Setx and _Carry are now directly private; they were previously inherited privately.
_Carry is now a direct data member.
Simplify _Swc_traits::_Reset() as _Readcy is always false.
Fuse _Swc_traits _Cy and _Mod, avoiding shadowing in _Write_full()!
- Also drop now-unused _Mod_t and _Seed_t.
Fuse _Swc_traits _Write_full().
Finish fusing _Swc_traits.
- _Reset() and _Reduce() are becoming non-static member functions.
Fuse _Reset() into seed().
Consistently use %=.

`subtract_with_carry_engine` Representation

I verified that subtract_with_carry_engine's representation isn't being changed by removing _Swc_base inheritance. I checked 32-bit and 64-bit engines, on both x64 and x86. I compared against the MSVC Build Tools 14.50 Preview 1, so the differences here also include #5712's recent removal of TR1 subtract_with_carry inheritance.

Click to expand test case and output:

Test Case

C:\Temp>type meow.cpp

#include <print>
#include <random>
using namespace std;

struct Test1 : ranlux24_base {};
struct Test2 : ranlux48_base {};

int main() {
    println("Arch: {}-bit; _MSVC_STL_UPDATE: {}", sizeof(void*) * 8, _MSVC_STL_UPDATE);
    println("ranlux24_base: sizeof: {}; alignof: {}", sizeof(ranlux24_base), alignof(ranlux24_base));
    println("ranlux48_base: sizeof: {}; alignof: {}", sizeof(ranlux48_base), alignof(ranlux48_base));
}

C:\Temp>cl /EHsc /nologo /W4 /std:c++latest /MT /Od /d1reportSingleClassLayoutTest meow.cpp && meow
meow.cpp

Old x64

class Test1     size(200):
        +---
 0      | +--- (base class std::subtract_with_carry_engine<unsigned int,24,10,24>)
 0      | | +--- (base class std::subtract_with_carry<unsigned int,16777216,10,24>)
 0      | | | +--- (base class std::_Swc_base<unsigned int,10,24,struct std::_Swc_traits<unsigned int,16777216,24> >)
 0      | | | | +--- (base class std::_Circ_buf<unsigned int,24>)
 0      | | | | | _Idx
 4      | | | | | _Ax
        | | | | +---
196     | | | | _Carry
        | | | +---
        | | +---
        | +---
        +---

class Test2     size(208):
        +---
 0      | +--- (base class std::subtract_with_carry_engine<unsigned __int64,48,5,12>)
 0      | | +--- (base class std::subtract_with_carry<unsigned __int64,281474976710656,5,12>)
 0      | | | +--- (base class std::_Swc_base<unsigned __int64,5,12,struct std::_Swc_traits<unsigned __int64,281474976710656,12> >)
 0      | | | | +--- (base class std::_Circ_buf<unsigned __int64,12>)
 0      | | | | | _Idx
        | | | | | <alignment member> (size=4)
 8      | | | | | _Ax
        | | | | +---
200     | | | | _Carry
        | | | | <alignment member> (size=4)
        | | | +---
        | | +---
        | +---
        +---
Arch: 64-bit; _MSVC_STL_UPDATE: 202507
ranlux24_base: sizeof: 200; alignof: 4
ranlux48_base: sizeof: 208; alignof: 8

New x64

class Test1     size(200):
        +---
 0      | +--- (base class std::subtract_with_carry_engine<unsigned int,24,10,24>)
 0      | | +--- (base class std::_Circ_buf<unsigned int,24>)
 0      | | | _Idx
 4      | | | _Ax
        | | +---
196     | | _Carry
        | +---
        +---

class Test2     size(208):
        +---
 0      | +--- (base class std::subtract_with_carry_engine<unsigned __int64,48,5,12>)
 0      | | +--- (base class std::_Circ_buf<unsigned __int64,12>)
 0      | | | _Idx
        | | | <alignment member> (size=4)
 8      | | | _Ax
        | | +---
200     | | _Carry
        | | <alignment member> (size=4)
        | +---
        +---
Arch: 64-bit; _MSVC_STL_UPDATE: 202510
ranlux24_base: sizeof: 200; alignof: 4
ranlux48_base: sizeof: 208; alignof: 8

Old x86

class Test1     size(200):
        +---
 0      | +--- (base class std::subtract_with_carry_engine<unsigned int,24,10,24>)
 0      | | +--- (base class std::subtract_with_carry<unsigned int,16777216,10,24>)
 0      | | | +--- (base class std::_Swc_base<unsigned int,10,24,struct std::_Swc_traits<unsigned int,16777216,24> >)
 0      | | | | +--- (base class std::_Circ_buf<unsigned int,24>)
 0      | | | | | _Idx
 4      | | | | | _Ax
        | | | | +---
196     | | | | _Carry
        | | | +---
        | | +---
        | +---
        +---

class Test2     size(208):
        +---
 0      | +--- (base class std::subtract_with_carry_engine<unsigned __int64,48,5,12>)
 0      | | +--- (base class std::subtract_with_carry<unsigned __int64,281474976710656,5,12>)
 0      | | | +--- (base class std::_Swc_base<unsigned __int64,5,12,struct std::_Swc_traits<unsigned __int64,281474976710656,12> >)
 0      | | | | +--- (base class std::_Circ_buf<unsigned __int64,12>)
 0      | | | | | _Idx
        | | | | | <alignment member> (size=4)
 8      | | | | | _Ax
        | | | | +---
200     | | | | _Carry
        | | | | <alignment member> (size=4)
        | | | +---
        | | +---
        | +---
        +---
Arch: 32-bit; _MSVC_STL_UPDATE: 202507
ranlux24_base: sizeof: 200; alignof: 4
ranlux48_base: sizeof: 208; alignof: 8

New x86

class Test1     size(200):
        +---
 0      | +--- (base class std::subtract_with_carry_engine<unsigned int,24,10,24>)
 0      | | +--- (base class std::_Circ_buf<unsigned int,24>)
 0      | | | _Idx
 4      | | | _Ax
        | | +---
196     | | _Carry
        | +---
        +---

class Test2     size(208):
        +---
 0      | +--- (base class std::subtract_with_carry_engine<unsigned __int64,48,5,12>)
 0      | | +--- (base class std::_Circ_buf<unsigned __int64,12>)
 0      | | | _Idx
        | | | <alignment member> (size=4)
 8      | | | _Ax
        | | +---
200     | | _Carry
        | | <alignment member> (size=4)
        | +---
        +---
Arch: 32-bit; _MSVC_STL_UPDATE: 202510
ranlux24_base: sizeof: 200; alignof: 4
ranlux48_base: sizeof: 208; alignof: 8

…:_Write()`. They were unused by `subtract_with_carry_engine`.

They were unused by `subtract_with_carry_engine`.

We don't need to `static_cast` when calling `_Left._Equals(_Right)`.

…ct_with_carry_engine` to make fusion easier and avoid shadowing.

They were unused.

Avoid redundant seeding in `subtract_with_carry_engine(_Seed_seq&)`.

`_Readcy` was always `false`.

Note that `_Setx` and `_Carry` are now directly `private`; they were previously inherited privately.

…ll()`! Also drop now-unused `_Mod_t` and `_Seed_t`.

`_Reset()` and `_Reduce()` are becoming non-static member functions.

StephanTLavavej · 2025-10-09T10:06:09Z

I'm mirroring this to the MSVC-internal repo - please notify me if any further changes are pushed.

davidmrdavid

LGTM, just a question and a non-blocking ultra-nit suggestion
Also:

👏 👏 👏

davidmrdavid · 2025-10-09T17:21:49Z

tests/std/tests/GH_002206_unreserved_names/test.compile.pass.cpp

 #define xtime            delete
 #define xtime_get        delete

+#define discard_block       delete


this is a new trick to me: what's the purpose of these macros mapping to delete (and previously to known constants)?

It ensures that if we ever mention them in our headers, the test will catastrophically fail to compile.

The #define meow 1729 ones are for when we want to mention them (because they're non-Standard extensions), but need to push-undef-pop, and at the end we check that the specific macro value has been restored.

This test is probably overkill but it's cheap to maintain.

stl/inc/random

StephanTLavavej added 24 commits October 3, 2025 22:29

Require Standard URBGs, delete machinery for TR1 generators.

d0a49f5

Remove _HAS_TR1_NAMESPACE.

168a5f1

Remove _SILENCE_TR1_NAMESPACE_DEPRECATION_WARNING.

50deac8

Remove _SILENCE_TR1_RANDOM_DEPRECATION_WARNING.

24baecb

Simplify test for removed non-Standard names.

8c431f9

Drop _Swc_base operator>>() and operator<<(), and `_Swc_traits:…

04f22b5

…:_Write()`. They were unused by `subtract_with_carry_engine`.

Drop _Swc_base min() and max(), and _Swc_traits::_Max.

785aa50

They were unused by `subtract_with_carry_engine`.

Fuse _Swc_base operator()() with strengthened noexcept.

8d2f894

Fuse _Swc_base discard().

58054da

Fuse _Swc_base operator==().

02a6f8c

We don't need to `static_cast` when calling `_Left._Equals(_Right)`.

Fuse _Swc_base default_seed.

aa04aff

Introduce and consistently use _Mytraits in _Swc_base and `subtra…

6d1aacc

…ct_with_carry_engine` to make fusion easier and avoid shadowing.

Fuse _Swc_base _Write_full().

5f8798e

Drop _Swc_base default ctor and ctor/seed() from _Gen&.

b388b08

They were unused.

Fuse _Swc_base construction.

8d3a924

Avoid redundant seeding in `subtract_with_carry_engine(_Seed_seq&)`.

Fuse _Swc_base seed().

3b35f57

`_Readcy` was always `false`.

Finish fusing _Swc_base.

33dc8d1

Note that `_Setx` and `_Carry` are now directly `private`; they were previously inherited privately.

_Carry is now a direct data member.

46260b6

Simplify _Swc_traits::_Reset() as _Readcy is always false.

35f43e6

Fuse _Swc_traits _Cy and _Mod, avoiding shadowing in `_Write_fu…

2126631

…ll()`! Also drop now-unused `_Mod_t` and `_Seed_t`.

Fuse _Swc_traits _Write_full().

03d59d4

Finish fusing _Swc_traits.

55c4244

`_Reset()` and `_Reduce()` are becoming non-static member functions.

Fuse _Reset() into seed().

6727c66

Consistently use %=.

dc6f590

StephanTLavavej requested a review from a team as a code owner October 4, 2025 20:21

StephanTLavavej added the enhancement Something can be improved label Oct 4, 2025

github-project-automation bot moved this to Initial Review in STL Code Reviews Oct 4, 2025

github-project-automation bot added this to STL Code Reviews Oct 4, 2025

StephanTLavavej moved this from Initial Review to Final Review in STL Code Reviews Oct 4, 2025

StephanTLavavej mentioned this pull request Oct 8, 2025

Google Test 1.7.0 is severely outdated and should be upgraded bulletphysics/bullet3#4746

Open

StephanTLavavej mentioned this pull request Oct 8, 2025

Google Test 1.6.0 is severely outdated and should be upgraded TorqueGameEngines/Torque2D#74

Open

davidmrdavid approved these changes Oct 9, 2025

View reviewed changes

StephanTLavavej moved this from Final Review to Merging in STL Code Reviews Oct 9, 2025

StephanTLavavej merged commit 7d6e34a into microsoft:main Oct 10, 2025
39 checks passed

github-project-automation bot moved this from Merging to Done in STL Code Reviews Oct 10, 2025

StephanTLavavej deleted the tr-none branch October 10, 2025 10:05

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Remove non-Standard TR1 #5763

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StephanTLavavej commented Oct 4, 2025

Overview

Commits

subtract_with_carry_engine Representation

Test Case

Old x64

New x64

Old x86

New x86

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