[libc++] Fix missing and incorrect push/pop macros (#79204)

We recently noticed that the unwrap_iter.h file was pushing macros, but
it was pushing them again instead of popping them at the end of the
file. This led to libc++ basically swallowing any custom definition of
these macros in user code:

    #define min HELLO
    #include <algorithm>
    // min is not HELLO anymore, it's not defined

While investigating this issue, I noticed that our push/pop pragmas were
actually entirely wrong too. Indeed, instead of pushing macros like
`move`, we'd push `move(int, int)` in the pragma, which is not a valid
macro name. As a result, we would not actually push macros like `move`
-- instead we'd simply undefine them. This led to the following code not
working:

    #define move HELLO
    #include <algorithm>
    // move is not HELLO anymore

Fixing the pragma push/pop incantations led to a cascade of issues
because we use identifiers like `move` in a large number of places, and
all of these headers would now need to do the push/pop dance.

This patch fixes all these issues. First, it adds a check that we don't
swallow important names like min, max, move or refresh as explained
above. This is done by augmenting the existing
system_reserved_names.gen.py test to also check that the macros are what
we expect after including each header.

Second, it fixes the push/pop pragmas to work properly and adds missing
pragmas to all the files I could detect a failure in via the newly added
test.

rdar://121365472

5 files changed, 25 insertions, 0 deletions

diff --git a/libcxx/include/__numeric/pstl_reduce.h b/libcxx/include/__numeric/pstl_reduce.h
index b19972a..f9f666c 100644
--- a/libcxx/include/__numeric/pstl_reduce.h
+++ b/libcxx/include/__numeric/pstl_reduce.h
@@ -20,6 +20,9 @@
 #  pragma GCC system_header
 #endif
 
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
 #if !defined(_LIBCPP_HAS_NO_INCOMPLETE_PSTL) && _LIBCPP_STD_VER >= 17
 
 _LIBCPP_BEGIN_NAMESPACE_STD
@@ -101,4 +104,6 @@ _LIBCPP_END_NAMESPACE_STD
 
 #endif // !defined(_LIBCPP_HAS_NO_INCOMPLETE_PSTL) && _LIBCPP_STD_VER >= 17
 
+_LIBCPP_POP_MACROS
+
 #endif // _LIBCPP___NUMERIC_PSTL_REDUCE_H
diff --git a/libcxx/include/__numeric/pstl_transform_reduce.h b/libcxx/include/__numeric/pstl_transform_reduce.h
index 1127726..2f412d4 100644
--- a/libcxx/include/__numeric/pstl_transform_reduce.h
+++ b/libcxx/include/__numeric/pstl_transform_reduce.h
@@ -22,6 +22,9 @@
 #  pragma GCC system_header
 #endif
 
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
 #if !defined(_LIBCPP_HAS_NO_INCOMPLETE_PSTL) && _LIBCPP_STD_VER >= 17
 
 _LIBCPP_BEGIN_NAMESPACE_STD
@@ -148,4 +151,6 @@ _LIBCPP_END_NAMESPACE_STD
 
 #endif // !defined(_LIBCPP_HAS_NO_INCOMPLETE_PSTL) && _LIBCPP_STD_VER >= 17
 
+_LIBCPP_POP_MACROS
+
 #endif // _LIBCPP___NUMERIC_PSTL_TRANSFORM_REDUCE_H
diff --git a/libcxx/include/__numeric/reduce.h b/libcxx/include/__numeric/reduce.h
index 1aeefce..6c205bf 100644
--- a/libcxx/include/__numeric/reduce.h
+++ b/libcxx/include/__numeric/reduce.h
@@ -19,6 +19,9 @@
 #  pragma GCC system_header
 #endif
 
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 #if _LIBCPP_STD_VER >= 17
@@ -45,4 +48,6 @@ reduce(_InputIterator __first, _InputIterator __last) {
 
 _LIBCPP_END_NAMESPACE_STD
 
+_LIBCPP_POP_MACROS
+
 #endif // _LIBCPP___NUMERIC_REDUCE_H
diff --git a/libcxx/include/__numeric/saturation_arithmetic.h b/libcxx/include/__numeric/saturation_arithmetic.h
index 50274c6..0e6f455 100644
--- a/libcxx/include/__numeric/saturation_arithmetic.h
+++ b/libcxx/include/__numeric/saturation_arithmetic.h
@@ -19,6 +19,9 @@
 #  pragma GCC system_header
 #endif
 
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 #if _LIBCPP_STD_VER >= 26
@@ -107,4 +110,6 @@ _LIBCPP_HIDE_FROM_ABI constexpr _Rp saturate_cast(_Tp __x) noexcept {
 
 _LIBCPP_END_NAMESPACE_STD
 
+_LIBCPP_POP_MACROS
+
 #endif // _LIBCPP___NUMERIC_SATURATION_ARITHMETIC_H
diff --git a/libcxx/include/__numeric/transform_reduce.h b/libcxx/include/__numeric/transform_reduce.h
index 6c0a81e..f115051 100644
--- a/libcxx/include/__numeric/transform_reduce.h
+++ b/libcxx/include/__numeric/transform_reduce.h
@@ -18,6 +18,9 @@
 #  pragma GCC system_header
 #endif
 
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 #if _LIBCPP_STD_VER >= 17
@@ -51,4 +54,6 @@ transform_reduce(_InputIterator1 __first1, _InputIterator1 __last1, _InputIterat
 
 _LIBCPP_END_NAMESPACE_STD
 
+_LIBCPP_POP_MACROS
+
 #endif // _LIBCPP___NUMERIC_TRANSFORM_REDUCE_H