Removing last remnants of pragma block at the top of pybind11.h (#3186)

* Removing last remnants of pragma block at the top of pybind11.h, defaulting CUDA, GCC7, GCC8 to PYBIND11_NOINLINE_DISABLED, with the option to define PYBIND11_NOINLINE_FORCED.

* Unique SOSIZE prefix to make it easier to extract the sosizes from the GitHub logs.

* Commenting out PYBIND11_WERROR block, for noinline testing.

* Undoing accidental change.

* `#define PYBIND11_NOINLINE_FORCED`

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* `#define PYBIND11_NOINLINE_DISABLED`

* Going back to default (removing `#define PYBIND11_NOINLINE_DISABLED`).

* `#define PYBIND11_NOINLINE_FORCED`

* Undoing all changes releated to measuring sosizes.

* Rollback of PR #3030 (Working around Centos 8 failure).

* Disabling -Werror for GNU (experiment).

* Commenting out the entire `if(PYBIND11_WERROR)` again (although that is not expected to make a difference, but who knows what I am overlooking).

* Adding `-DCMAKE_BUILD_TYPE=Release`

* Undoing change to tests/CMakeLists.txt (uncommenting `if(PYBIND11_WERROR)` block).

* post `git rebase master -X theirs` fixups.

* Adding measurements to comment for `PYBIND11_NOINLINE_FORCED`.

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

include/pybind11/detail/common.h

@@ -99,6 +99,17 @@
 #  endif
 #endif
 
+// For CUDA, GCC7, GCC8:
+// PYBIND11_NOINLINE_FORCED is incompatible with `-Wattributes -Werror`.
+// When defining PYBIND11_NOINLINE_FORCED, it is best to also use `-Wno-attributes`.
+// However, the measured shared-library size saving when using noinline are only
+// 1.7% for CUDA, -0.2% for GCC7, and 0.0% for GCC8 (using -DCMAKE_BUILD_TYPE=MinSizeRel,
+// the default under pybind11/tests).
+#if !defined(PYBIND11_NOINLINE_FORCED) && \
+    (defined(__CUDACC__) || (defined(__GNUC__) && (__GNUC__ == 7 || __GNUC__ == 8)))
+#  define PYBIND11_NOINLINE_DISABLED
+#endif
+
 // The PYBIND11_NOINLINE macro is for function DEFINITIONS.
 // In contrast, FORWARD DECLARATIONS should never use this macro:
 // https://stackoverflow.com/questions/9317473/forward-declaration-of-inline-functions

include/pybind11/pybind11.h

@@ -10,11 +10,6 @@
 
 #pragma once
 
-#if defined(__CUDACC__) || (defined(__GNUC__) && (__GNUC__ == 7 || __GNUC__ == 8))
-#  pragma GCC diagnostic push
-#  pragma GCC diagnostic ignored "-Wattributes"
-#endif
-
 #include "attr.h"
 #include "gil.h"
 #include "options.h"
@@ -2383,7 +2378,3 @@ PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)
 #if defined(__GNUC__) && __GNUC__ == 7
 #    pragma GCC diagnostic pop // -Wnoexcept-type
 #endif
-
-#if defined(__CUDACC__) || (defined(__GNUC__) && (__GNUC__ == 7 || __GNUC__ == 8))
-#  pragma GCC diagnostic pop
-#endif