Disable -Wstringop-overflow in --enable-optimized builds with GCC

This reverts commit e287fde52fb9de5bdf1d00c8a3fbfcca7db9892c "Silence bogus
-Wstringop-overflow with GCC trunk towards GCC 10", as that workaround, which
happened to work for some revisions of GCC trunk towards GCC 10, no longer works
for GCC 10 release candidates, see
<https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92893#c9> "[10 Regression]
Unhelpful -Wstringop-overflow warning for a trailing one-element array".

(Using -Wstringop-overflow=1 instead of the -Wstringop-overflow=2 default would
have still caused bogus warnings, requiring -Wno-stringop-overflow.)

Change-Id: I9b7342748c18da32f509b4a0e0653aede8447657
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/93499
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>

4 files changed, 3 insertions, 40 deletions

diff --git a/include/rtl/strbuf.hxx b/include/rtl/strbuf.hxx
index e9a548297016..2a303ce998e6 100644
--- a/include/rtl/strbuf.hxx
+++ b/include/rtl/strbuf.hxx
@@ -569,15 +569,7 @@ public:
             return *this;
         l += pData->length;
         rtl_stringbuffer_ensureCapacity( &pData, &nCapacity, l );
-#if defined __GNUC__ && __GNUC__ == 10 && !defined __clang__
-        // Avoid some bogus GCC 10 trunk -Werror=stringop-overflow (see
-        // <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92893> "Unhelpful -Wstringop-overflow
-        // warning"):
-        struct Hack { char c; char a[]; };
-        char* end = c.addData( &reinterpret_cast<Hack *>(pData->buffer)->c + pData->length );
-#else
         char* end = c.addData( pData->buffer + pData->length );
-#endif
         *end = '\0';
         pData->length = l;
         return *this;
diff --git a/include/rtl/string.hxx b/include/rtl/string.hxx
index 4f600affdabe..809b0a11bcd5 100644
--- a/include/rtl/string.hxx
+++ b/include/rtl/string.hxx
@@ -273,15 +273,7 @@ public:
         pData = rtl_string_alloc( l );
         if (l != 0)
         {
-#if defined __GNUC__ && __GNUC__ == 10 && !defined __clang__
-            // Avoid some bogus GCC 10 trunk -Werror=stringop-overflow (see
-            // <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92893> "Unhelpful -Wstringop-overflow
-            // warning"):
-            struct Hack { char c; char a[]; };
-            char* end = c.addData( &reinterpret_cast<Hack *>(pData->buffer)->c );
-#else
             char* end = c.addData( pData->buffer );
-#endif
             pData->length = l;
             *end = '\0';
         }
@@ -389,15 +381,7 @@ public:
             return *this;
         l += pData->length;
         rtl_string_ensureCapacity( &pData, l );
-#if defined __GNUC__ && __GNUC__ == 10 && !defined __clang__
-        // Avoid some bogus GCC 10 trunk -Werror=stringop-overflow (see
-        // <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92893> "Unhelpful -Wstringop-overflow
-        // warning"):
-        struct Hack { char c; char a[]; };
-        char* end = c.addData( &reinterpret_cast<Hack *>(pData->buffer)->c + pData->length );
-#else
         char* end = c.addData( pData->buffer + pData->length );
-#endif
         *end = '\0';
         pData->length = l;
         return *this;
diff --git a/include/rtl/ustring.hxx b/include/rtl/ustring.hxx
index ffe42d139215..5f0c1032c603 100644
--- a/include/rtl/ustring.hxx
+++ b/include/rtl/ustring.hxx
@@ -401,15 +401,7 @@ public:
         pData = rtl_uString_alloc( l );
         if (l != 0)
         {
-#if defined __GNUC__ && __GNUC__ == 10 && !defined __clang__
-            // Avoid some bogus GCC 10 trunk -Werror=stringop-overflow (see
-            // <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92893> "Unhelpful -Wstringop-overflow
-            // warning"):
-            struct Hack { sal_Unicode c; sal_Unicode a[]; };
-            sal_Unicode* end = c.addData( reinterpret_cast<Hack *>(pData->buffer - 1)->a );
-#else
             sal_Unicode* end = c.addData( pData->buffer );
-#endif
             pData->length = l;
             *end = '\0';
             // TODO realloc in case pData->length is noticeably smaller than l?
@@ -638,15 +630,7 @@ public:
             return *this;
         l += pData->length;
         rtl_uString_ensureCapacity( &pData, l );
-#if defined __GNUC__ && __GNUC__ == 10 && !defined __clang__
-        // Avoid some bogus GCC 10 trunk -Werror=stringop-overflow (see
-        // <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92893> "Unhelpful -Wstringop-overflow
-        // warning"):
-        struct Hack { sal_Unicode c; sal_Unicode a[]; };
-        sal_Unicode* end = c.addData( reinterpret_cast<Hack *>(pData->buffer - 1)->a + pData->length );
-#else
         sal_Unicode* end = c.addData( pData->buffer + pData->length );
-#endif
         *end = '\0';
         pData->length = l;
         return *this;
diff --git a/solenv/gbuild/platform/com_GCC_defs.mk b/solenv/gbuild/platform/com_GCC_defs.mk
index baeb215bfb9e..4d3602864bc8 100644
--- a/solenv/gbuild/platform/com_GCC_defs.mk
+++ b/solenv/gbuild/platform/com_GCC_defs.mk
@@ -162,6 +162,9 @@ endif
 endif
 
 gb_CFLAGS_WERROR = $(if $(ENABLE_WERROR),-Werror)
+ifeq ($(ENABLE_OPTIMIZED)-$(COM_IS_CLANG),TRUE-)
+gb_CFLAGS_WERROR += -Wno-stringop-overflow
+endif
 
 # This is the default in non-C++11 mode
 ifeq ($(COM_IS_CLANG),TRUE)