Add cppdemangle in druntime #3002

ErnyTech · 2020-03-24T18:23:54Z

Add cppdemangle in druntime

Having a C++ symbol demangler is very useful, with this it will
be possible to implement the C++ symbol demangle in the stacktrace.

The demangling is done in Posix platform by function __cxa_demangle
presents in Itanium C++ ABI (https://itanium-cxx-abi.github.io/cxx-abi/abi.html#demangler).

Itanium C++ ABI is used practically in all modern C++ compilers on Posix,
however old compilers (like GCC < 3.0) used a different name mangling,
this is not a problem because DMD in fact only supports Itanium C++ ABI on Posix.

For Windows instead the implementation it is provided by the UnDecorateSymbolName
function present in the Debug Help Library.
(https://docs.microsoft.com/en-us/windows/win32/api/dbghelp/nf-dbghelp-undecoratesymbolname)

dlang-bot · 2020-03-25T15:55:57Z

Thanks for your pull request and interest in making D better, @ErnyTech! We are looking forward to reviewing it, and you should be hearing from a maintainer soon.
Please verify that your PR follows this checklist:

My PR is fully covered with tests (you can see the coverage diff by visiting the details link of the codecov check)
My PR is as minimal as possible (smaller, focused PRs are easier to review than big ones)
I have provided a detailed rationale explaining my changes
New or modified functions have Ddoc comments (with Params: and Returns:)

Please see CONTRIBUTING.md for more information.

If you have addressed all reviews or aren't sure how to proceed, don't hesitate to ping us with a simple comment.

Bugzilla references

Your PR doesn't reference any Bugzilla issue.

If your PR contains non-trivial changes, please reference a Bugzilla issue or create a manual changelog.

Testing this PR locally

If you don't have a local development environment setup, you can use Digger to test this PR:

dub run digger -- build "master + druntime#3002"

ErnyTech · 2020-04-01T12:35:37Z

It is now ready for review.

Geod24

Did a first round of review

src/core/internal/cppdemangle.d

Geod24 · 2020-04-01T17:03:50Z

src/core/internal/cppdemangle.d

+        version (Posix)
+        {
+            int result;
+            auto demangledNamePtr = _instance.__cxa_demangle(mangledName, null, null, &result);


I don't see the point of copying the result when you could just pass the pointer to the array here ?

ErnyTech · 2020-04-01T17:37:39Z

Thanks for the extensive review!

ErnyTech · 2020-04-12T20:34:25Z

@Geod24, this is ready for second round ;-)

Having a C++ symbol demangler is very useful, with this it will be possible to implement the C++ symbol demangle in the stacktrace. The demangling is done in Posix platform by function __cxa_demangle presents in Itanium C++ ABI (https://itanium-cxx-abi.github.io/cxx-abi/abi.html#demangler). Itanium C++ ABI is used practically in all modern C++ compilers on Posix, however old compilers (like GCC < 3.0) used a different name mangling, this is not a problem because DMD in fact only supports Itanium C++ ABI on Posix. For Windows instead the implementation it is provided by the UnDecorateSymbolName function present in the Debug Help Library. (https://docs.microsoft.com/en-us/windows/win32/api/dbghelp/nf-dbghelp-undecoratesymbolname) Signed-off-by: Ernesto Castellotti <mail@ernestocastellotti.it>

MoonlightSentinel · 2020-06-11T13:09:38Z

src/core/internal/cppdemangle.d

+/**
+* Demangles C++ mangled names.
+*
+* The output buffer and return will be contains the demangled name of C++ symbol if the demangling is successful.


Suggested change

* The output buffer and return will be contains the demangled name of C++ symbol if the demangling is successful.

* The output buffer and return value will contain the demangled name of C++ symbol if the demangling is successful.

MoonlightSentinel · 2020-06-11T13:12:10Z

src/core/internal/cppdemangle.d

+*
+* The output buffer and return will be contains the demangled name of C++ symbol if the demangling is successful.
+*
+* This function will fail and the mangled name in input will be returned if:


I think the "return input on failure" part should be mentioned in the previous sentence as it describes the general function contract

MoonlightSentinel · 2020-06-11T13:16:19Z

src/core/internal/cppdemangle.d

+*
+ * Params:
+ *  mangledName = The string to demangle.
+ *  outputBuffer = The destination buffer, if the size of the destination buffer is <= the size of cppdemangle output the return string would be incomplete.


Redundant size requirement, it's already mentioned above

MoonlightSentinel · 2020-06-11T13:21:12Z

src/core/internal/cppdemangle.d

+ * Returns:
+ *  The demangled name or the original string if the name is not a mangled C++ name.
+ */
+char[] cppdemangle(const(char)[] mangledName, char[] outputBuffer, string prefix = "") @trusted


Don't think this function should accept a prefix, it's an unrelated complication and a user can always do that manually:

buffer[0..prefix.length] = prefix; cppdemangle(mangling, buffer[prefix.length .. $]);

MoonlightSentinel · 2020-06-11T13:21:56Z

src/core/internal/cppdemangle.d

+ * Returns:
+ *  The demangled name or the original string if the name is not a mangled C++ name.
+ */
+char[] cppdemangle(const(char)[] mangledName, char[] outputBuffer, string prefix = "") @trusted


The symbol should be in camelCase: cppDemangle

@trusted should probably be used in smaller scope(s).

MoonlightSentinel · 2020-06-11T13:30:38Z

src/core/internal/cppdemangle.d

+        @nogc nothrow extern(System)
+        {
+            private UnDecorateSymbolNameFunc UnDecorateSymbolName;
+        }


@nogc nothrow extern(System) doesn't affect the type of UnDecorateSymbolName and extern(System) is redundant anyway

MoonlightSentinel · 2020-06-11T13:31:02Z

src/core/internal/cppdemangle.d

+        }
+    }
+
+    version (Windows)


Suggested change

version (Windows)

else version (Windows)

ErnyTech · 2020-06-24T16:21:50Z

Now that my exams are over I can continue with this!
Thanks for the review @MoonlightSentinel

MoonlightSentinel · 2021-12-06T19:14:27Z

Ping @ErnyTech

ljmf00

Just a note to tick later: Missing tests.

ljmf00 · 2021-12-06T19:39:51Z

src/core/internal/cppdemangle.d

+            private static immutable names = ["libc++abi.dylib", "libstdc++.dylib"];
+        else
+        {
+            private static immutable names = ["libstdc++.so", "libstdc++.so.6", "libstdc++.so.5",


What about fallbacks to other major versions of libstdc++? It shouldn't be required for new systems but could be good for compatibility.

ljmf00 · 2021-12-06T19:47:11Z

src/core/internal/cppdemangle.d

+
+        @nogc nothrow extern(System)
+        {
+            private UnDecorateSymbolNameFunc UnDecorateSymbolName;


UnDecorateSymbolName is a symbol from dbghelp.dll and that doesn't come with a Windows stock installation, being instead, part of Windows Debugging Kit (WDK). Also, considering MinGW systems, aren't libstdc++ shipped anyway? Notwithstanding, we should have fallbacks for those too, just in case.

ljmf00 · 2021-12-06T19:49:42Z

src/core/internal/cppdemangle.d

+        {
+            import core.sys.posix.dlfcn : dlsym, dlopen, dlclose, RTLD_LAZY;
+
+            auto handle = dlopen(null, RTLD_LAZY);


Why not add null to the fallback list instead of doing code duplication? Is there any additional logic I'm missing here?

ljmf00 · 2021-12-06T19:56:31Z

src/core/internal/cppdemangle.d

+            return null;
+        }
+
+        auto mangledNamePtr = cast(char*) pureCalloc(mangledName.length + 1, char.sizeof);


Please check if the allocation succeed.

ljmf00 · 2021-12-06T19:59:10Z

src/core/internal/cppdemangle.d

+                }
+            }
+
+            return copyResult(demangledName[0..strlen(demangledName)], outputBuffer);


Please don't do strlen. __cxa_demangle is capable of returning the length. See https://gcc.gnu.org/onlinedocs/libstdc++/libstdc++-html-USERS-4.3/a01696.html

Why do we use a copyResult function in the first place? We shouldn't hang if the buffer is not large enough, and could return the allocated buffer directly if the provided output buffer is null.

ljmf00 · 2021-12-06T20:04:42Z

src/core/internal/cppdemangle.d

+        version (Posix)
+        {
+            int status;
+            auto demangledName = _instance.__cxa_demangle(mangledNamePtr, null, null, &status);


Please feed the output buffer to __cxa_demangle since a preallocated buffer can help avoid unnecessary reallocations.

This was referenced Mar 24, 2020

Add cppdemangle in druntime #2803

Closed

[WIP] [DONT MERGE] Enable demangling of C++ symbols in the stacktrace #3003

Draft

ErnyTech marked this pull request as ready for review March 24, 2020 21:46

ErnyTech requested review from andralex, MartinNowak, schveiguy and wilzbach as code owners March 24, 2020 21:46

ErnyTech force-pushed the cppdemangle branch from 79e7a7c to 115ff06 Compare March 25, 2020 15:55

ErnyTech force-pushed the cppdemangle branch 2 times, most recently from 36d80f7 to 1be511b Compare March 26, 2020 14:30

ErnyTech changed the title ~~Add cppdemangle in druntime~~ [WIP] Add cppdemangle in druntime Mar 27, 2020

dlang-bot added the WIP Work In Progress - not ready for review or pulling label Mar 27, 2020

ErnyTech force-pushed the cppdemangle branch 6 times, most recently from cb69e57 to 0de39b0 Compare April 1, 2020 11:15

ErnyTech changed the title ~~[WIP] Add cppdemangle in druntime~~ Add cppdemangle in druntime Apr 1, 2020

Geod24 suggested changes Apr 1, 2020

View reviewed changes

Geod24 removed the WIP Work In Progress - not ready for review or pulling label Apr 1, 2020

ErnyTech force-pushed the cppdemangle branch 6 times, most recently from bbe2da0 to f7e3b10 Compare April 12, 2020 19:33

ErnyTech requested a review from Geod24 April 12, 2020 20:38

ErnyTech force-pushed the cppdemangle branch from f7e3b10 to 2e92b4a Compare April 22, 2020 14:37

MoonlightSentinel suggested changes Jun 11, 2020

View reviewed changes

dlang-bot added the stalled label May 27, 2021

ljmf00 suggested changes Dec 6, 2021

View reviewed changes

dlang-bot removed the stalled label Dec 7, 2021

dlang-bot added the stalled label Mar 7, 2022

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

Add cppdemangle in druntime #3002

Add cppdemangle in druntime #3002

ErnyTech commented Mar 24, 2020 •

edited

dlang-bot commented Mar 25, 2020

ErnyTech commented Apr 1, 2020

Geod24 left a comment

Geod24 Apr 1, 2020

ErnyTech commented Apr 1, 2020

ErnyTech commented Apr 12, 2020 •

edited

MoonlightSentinel Jun 11, 2020

MoonlightSentinel Jun 11, 2020 •

edited

MoonlightSentinel Jun 11, 2020

MoonlightSentinel Jun 11, 2020

MoonlightSentinel Jun 11, 2020

MoonlightSentinel Jun 11, 2020

MoonlightSentinel Jun 11, 2020

MoonlightSentinel Jun 11, 2020

ErnyTech commented Jun 24, 2020 •

edited

MoonlightSentinel commented Dec 6, 2021

ljmf00 left a comment

ljmf00 Dec 6, 2021

ljmf00 Dec 6, 2021

ljmf00 Dec 6, 2021

ljmf00 Dec 6, 2021

ljmf00 Dec 6, 2021

ljmf00 Dec 6, 2021

	* The output buffer and return will be contains the demangled name of C++ symbol if the demangling is successful.
	* The output buffer and return value will contain the demangled name of C++ symbol if the demangling is successful.

Add cppdemangle in druntime #3002

Are you sure you want to change the base?

Add cppdemangle in druntime #3002

Conversation

ErnyTech commented Mar 24, 2020 • edited

dlang-bot commented Mar 25, 2020

Bugzilla references

Testing this PR locally

ErnyTech commented Apr 1, 2020

Geod24 left a comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

ErnyTech commented Apr 1, 2020

ErnyTech commented Apr 12, 2020 • edited

Choose a reason for hiding this comment

MoonlightSentinel Jun 11, 2020 • edited

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

ErnyTech commented Jun 24, 2020 • edited

MoonlightSentinel commented Dec 6, 2021

ljmf00 left a comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

ErnyTech commented Mar 24, 2020 •

edited

ErnyTech commented Apr 12, 2020 •

edited

MoonlightSentinel Jun 11, 2020 •

edited

ErnyTech commented Jun 24, 2020 •

edited