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From: "tanksherman27 at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/115230] New: -fvisibility=hidden does not hide Template
 Specializations from being exported
Date: Sun, 26 May 2024 07:38:24 +0000
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X-Bugzilla-Product: gcc
X-Bugzilla-Component: c++
X-Bugzilla-Version: 14.1.1
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X-Bugzilla-Severity: normal
X-Bugzilla-Who: tanksherman27 at gmail dot com
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X-Bugzilla-Priority: P3
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D115230

            Bug ID: 115230
           Summary: -fvisibility=3Dhidden does not hide Template
                    Specializations from being exported
           Product: gcc
           Version: 14.1.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: tanksherman27 at gmail dot com
  Target Milestone: ---

Consider the following code:

#include <cstdlib>

template<typename T>
void method(T* src, T* dst, size_t length);

template<>
void method<short>(short* src, short* dst, size_t length) {

}

template<>
void method<int>(int* src, int* dst, size_t length) {

}

Compiled using command line:
g++ -O3 -fvisibility=3Dhidden -std=3Dc++14 -pedantic -Wpedantic -Wall -Werr=
or
templates.cpp

Linked using:
g++ -shared -o libtemplates.so templates.o

When nm is run over it using nm -gDC libtemplates.so, the following symbols=
 are
seen:
                 w _ITM_deregisterTMCloneTable
                 w _ITM_registerTMCloneTable
0000000000001110 T void method<int>(int*, int*, unsigned long)
0000000000001100 T void method<short>(short*, short*, unsigned long)
                 w __cxa_finalize
                 w __gmon_start__

T void method<int>(int*, int*, unsigned long) and T void method<short>(shor=
t*,
short*, unsigned long) should not be in the symbol table, but they are even
with -fvisibility=3Dhidden.

Strangely, marking both methods with [[gnu::visibility("hidden")]] works and
results in both not being exported.

This was recently observed in the JDK, inside the Java HotSpot VM (see
https://github.com/openjdk/jdk/pull/17955/files#r1498933843)=