Print generated class/struct in C++ #3378

bernardnormier · 2025-01-17T00:55:33Z

This PR adds printing to generated structs and classes in C++, using operator<<(ostream&, const T&).

The implementation piggy backs on the existing StreamHelpers. It adds a new print function on the StreamHelper template. It also adds an Ice::print function that prints any mapped field type (see StreamHelpers.h).

This implementation detects cycles when printing classes, to avoid stack overflow.

This implementation also supports custom printing with the new ["cpp:custom-print"] metadata for structs and classes. For structs, the application needs to implement operator<<(ostream&, const T&), while for classes, the application needs to implement T::ice_print(ostream&) const.

bernardnormier · 2025-01-18T19:34:07Z

cpp/include/Ice/Proxy.h

@@ -860,6 +861,22 @@ namespace Ice
        IceInternal::ReferencePtr _reference;
        IceInternal::RequestHandlerCachePtr _requestHandlerCache;
    };
+
+    ICE_API std::ostream& operator<<(std::ostream&, const ObjectPrx&);


Moved from ProxyFunctions.h to Proxy.h, because the generated code "sees" Proxy.h but not ProxyFunctions.h

bernardnormier · 2025-01-18T19:34:56Z

cpp/include/Ice/StreamHelpers.h


 #if __has_include(<span>)
 #    include <span>
 #endif

+namespace std
+{
+    // TODO: temporary


Remove when #3372 is merged.

bernardnormier · 2025-01-18T19:43:33Z

cpp/test/Slice/print/AllTests.cpp

+    testPrint(
+        byteBoolStruct,
+        "Test::ByteBoolStruct{myByteSeq = [0x64, 0x96, 0xff], myBoolSeq = [true, false, true]}",
+        [](ostream& os) { os << hex << showbase; });


The user can easily change the formatting. The Ice "print" functions don't change the format flags of the stream.

bernardnormier · 2025-01-18T19:44:23Z

cpp/test/Slice/print/AllTests.cpp

+using namespace Test;
+
+void
+Test::Neighbor::ice_print(ostream& os) const


Example of custom class printing. For custom struct printing, see Ice::Identity, Ice::EncodingVersion.

pepone · 2025-01-20T09:11:15Z

cpp/include/Ice/Value.h

+    /// @param os The output stream.
+    /// @param value The class instance.
+    /// @return The output stream.
+    inline std::ostream& operator<<(std::ostream& os, const Value& value)


Do we need this Ice::Value by reference? Ice always passes Ice::Value using shared_ptr.

We don't strictly need it, but I think it's nicer and more consistent with mapped exceptions, where (an) operator<< is "equivalent" to ice_print. See #3380.

pepone · 2025-01-20T10:02:43Z

slice/Ice/Version.ice

@@ -13,6 +13,7 @@
 [["cpp:include:Ice/Config.h"]]
 [["cpp:include:Ice/Comparable.h"]]
 [["cpp:include:cstdint"]]
+[["cpp:include:ostream"]]


Why is this required?

Because we have above:

[["cpp:no-default-include"]]

which means all C++ includes must be explicit. And since we define structs, we always get:

void ice_printFields(std::ostream& os) const;

pepone · 2025-01-20T10:45:05Z

cpp/src/Ice/Value.cpp

+        deque<const Value*> _localStack;
+        deque<const Value*>* _currentStack{nullptr}; // may or may not point to _localStack
+
+        static const int _cycleCheckIndex;


Should this be a thread local?

No. See https://en.cppreference.com/w/cpp/io/ios_base/xalloc

I see the API is thread safe. There is still an issue that this would show already printed when same class is being printed by concurrent calls.

I am not following.

The index (an int) is global and thread-safe. The data we store (pointer to a deque) is per ostream instance and not shared by all ostream instances. And naturally, a given ostream instance is not supposed to be used concurrently from multiple threads.

Never mind you are right. I was missing that the allocation is done on a per stream with the pword call.

InsertCreativityHere

Looks good.
I'll let you merge first, then I guess I'll deal with the merge conflicts in my PR,
and remove the stop-gap you put in for enums.

InsertCreativityHere · 2025-01-20T16:35:05Z

cpp/src/DataStorm/TraceUtil.cpp

+
+// Our custom implementation of various operator<< for structs defined in Contract.ice
+
+namespace DataStormContract


It would be nice if these were in the same order as the Slice definitions, instead of a seemingly random order.
The Slice order:

struct DataSamples struct ElementInfo struct TopicInfo struct TopicSpec struct ElementData struct ElementSpec struct ElementDataAck struct ElementSpecAck

Nevermind, I didn't realize this was just moved from TraceUtil.h.

InsertCreativityHere · 2025-01-20T16:49:10Z

cpp/src/slice2cpp/Gen.cpp

@@ -772,16 +772,18 @@ Slice::Gen::generate(const UnitPtr& p)
        }
    }

-    if (!dc->hasMetadata("cpp:no-default-include"))
+    // Include Ice.h since it was not included in the header.


So, as of this PR, the only effect of cpp:no-default-includes is to move
#include <Ice/Ice.h>
from the header file to the source file?

InsertCreativityHere · 2025-01-20T16:54:11Z

cpp/src/slice2cpp/Gen.cpp

@@ -2317,8 +2379,7 @@ Slice::Gen::DataDefVisitor::visitClassDefEnd(const ClassDefPtr& p)
    C << nl << "return CloneEnabler<" << name << ">::clone(*this);";
    C << eb;

-    const string baseClass = base ? getUnqualified(base->mappedScoped(), scope) : getUnqualified("::Ice::Value", scope);
-
+    H << sp;


You added this to fix a formatting bug?

…eroc-ice/ice#3378)

bernardnormier added 4 commits January 15, 2025 12:28

First cut

f2db757

Merge remote-tracking branch 'origin/main' into ice_print

6aafeef

Initial impl of class/struct printing in C++

cfdf073

Reformat

962606a

bernardnormier marked this pull request as draft January 17, 2025 00:55

bernardnormier added 11 commits January 16, 2025 20:03

Fix wstring TODO

cbd29f2

Cleanup

beb3c95

Add cycle detection

925202c

Fix gcc build failure

bd1a38a

Add cpp:custom-print

ee61352

Add test

169a066

Add cpp:custom-print for classes

d9a8a28

Move print test to Slice

ea03cc7

Remove class prefix

c9001ae

Cleanup

70d1e7e

New CHANGELOG entry

8a53d47

bernardnormier changed the title ~~Initial impl of class/struct printing in C++~~ Print generated class/struct in C++ Jan 18, 2025

bernardnormier requested review from pepone, InsertCreativityHere and externl and removed request for pepone January 18, 2025 19:29

bernardnormier marked this pull request as ready for review January 18, 2025 19:30

bernardnormier added 2 commits January 18, 2025 14:30

Merge remote-tracking branch 'origin/main' into ice_print

2950e3d

Update CHANGELOG

d46f992

bernardnormier commented Jan 18, 2025

View reviewed changes

This was referenced Jan 18, 2025

Generate 'operator<<' Implementation for Slice-generated Enums #3372

Merged

Simplify C++ exceptions #3380

Merged

bernardnormier added 2 commits January 19, 2025 12:21

Cleanup

e3cc742

Simplify generated printFields

45d364d

Simplify further

0f03dd6

pepone approved these changes Jan 20, 2025

View reviewed changes

externl approved these changes Jan 20, 2025

View reviewed changes

bernardnormier added 2 commits January 20, 2025 10:59

More cleanup

96bd0d7

Merge remote-tracking branch 'origin/main' into ice_print

71c4d13

InsertCreativityHere approved these changes Jan 20, 2025

View reviewed changes

bernardnormier merged commit eecd42a into zeroc-ice:main Jan 20, 2025
23 of 24 checks passed

bernardnormier mentioned this pull request Jan 20, 2025

Print fields of C++ user exceptions #3388

Merged

InsertCreativityHere pushed a commit to InsertCreativityHere/compiler-comparison that referenced this pull request Jan 21, 2025

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…eroc-ice/ice#3378)

bernardnormier deleted the ice_print branch March 24, 2025 14:25

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Print generated class/struct in C++ #3378

Print generated class/struct in C++ #3378

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		// Our custom implementation of various operator<< for structs defined in Contract.ice

		namespace DataStormContract

Print generated class/struct in C++ #3378

Print generated class/struct in C++ #3378

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bernardnormier commented Jan 17, 2025 • edited Loading

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bernardnormier commented Jan 17, 2025 •

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