[Bug demangler/93035] New: Found 91 mangled names which do not demangle using c++filt
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93035 Bug ID: 93035 Summary: Found 91 mangled names which do not demangle using c++filt Product: gcc Version: 9.2.1 Status: UNCONFIRMED Severity: normal Priority: P3 Component: demangler Assignee: unassigned at gcc dot gnu.org Reporter: simonhf at gmail dot com Target Milestone: --- The list of mangled names failing to demangle with c++filt is here [1]. They also fail to demangle with the independently implemented c++filt.go [2]. However, they all demangle okay using llvm-cxxfilt [3]. $ llvm-cxxfilt --version | egrep version LLVM version 9.0.0 [1] https://github.com/ianlancetaylor/demangle/issues/10 [2] https://github.com/ianlancetaylor/demangle [3] https://llvm.org/docs/CommandGuide/llvm-cxxfilt.html
[Bug demangler/93035] Found 91 mangled names which do not demangle using c++filt
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93035 --- Comment #1 from Simon Hardy-Francis --- Also, for names which do demangle then there are wide spread differences [1] if the same name is demangled using llvm-cxxfilt. I tried out demangling over 100k mangled names with both tools here [1]. [1] https://gist.github.com/simonhf/0d60bb94f2d90c1b32e4786b2d1062ad
[Bug c++/93475] New: With 100k+ mangled names, appears to incorrectly mangle about 15% causing demangle failure
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93475 Bug ID: 93475 Summary: With 100k+ mangled names, appears to incorrectly mangle about 15% causing demangle failure Product: gcc Version: 9.2.1 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c++ Assignee: unassigned at gcc dot gnu.org Reporter: simonhf at gmail dot com Target Milestone: --- When looking at over 100k mangled C++ names, many of them fail to demangle using common command line tools. Initially I thought this was the fault of the demangler and opened a bug here [1]. However, after opening a similar bug here [2] for the LLVM demangler, a detailed response from LLVM developers appears to suggest that g++ itself is mangling incorrect, so I opened this bug! [1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93035 [2] https://bugs.llvm.org/show_bug.cgi?id=44428
[Bug c++/93475] With 100k+ mangled names, g++ appears to incorrectly mangle about 15% causing demangle failure
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93475 --- Comment #2 from Simon Hardy-Francis --- The other two links posted link to this gist [1] which contains a list of the presumably incorrectly mangled names which fail to demangle. The mangled names were harvested from g++ assembly files after compiling this open source project called Zeek [2]. Link [1] contains the list of mangled names which fail to demangle and which the LLVM guys suggest were incorrectly mangled in the first place. If you'd like to recreate the list then recompile Zeek [2] via assembly files and then harvest the mangled names from the assembly files. Friendly warning: Many of the mangled names are many KB long, and many of the demangled names are many 100 KB long due to gratuitous C++ templating! Good luck! [1] https://gist.github.com/simonhf/0d60bb94f2d90c1b32e4786b2d1062ad [2] https://github.com/zeek/zeek
[Bug rtl-optimization/47712] New: optimization (-O) of code using union unexpectedly causes essential code to be optimized away
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47712
Summary: optimization (-O) of code using union unexpectedly
causes essential code to be optimized away
Product: gcc
Version: 4.5.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: rtl-optimization
AssignedTo: unassig...@gcc.gnu.org
ReportedBy: simo...@gmail.com
Reproduce with:
mingw32-gcc.exe -DWITH_UNNECESSARY_CODEexample.c -oexample.exe &&
example.exe
mingw32-gcc.exeexample.c -oexample.exe &&
example.exe
mingw32-gcc.exe -DWITH_UNNECESSARY_CODE -O example.c -oexample.exe &&
example.exe
mingw32-gcc.exe -O example.c -oexample.exe &&
example.exe
Shows output:
C:\20110211-gcc-bug>mingw32-gcc.exe -DWITH_UNNECESSARY_CODEexample.c
-oexample.exe && example.exe
before copy_bytes(): source : abcd
before copy_bytes(): destination: 1234
calling copy_bytes(): copy source to destination
after copy_bytes(): source : abcd
after copy_bytes(): destination: abcd <-- expected
C:\20110211-gcc-bug>mingw32-gcc.exeexample.c
-oexample.exe && example.exe
before copy_bytes(): source : abcd
before copy_bytes(): destination: 1234
calling copy_bytes(): copy source to destination
after copy_bytes(): source : abcd
after copy_bytes(): destination: abcd <-- expected
C:\20110211-gcc-bug>mingw32-gcc.exe -DWITH_UNNECESSARY_CODE -O example.c
-oexample.exe && example.exe
before copy_bytes(): source : abcd
before copy_bytes(): destination: 1234
calling copy_bytes(): copy source to destination
after copy_bytes(): source : abcd
after copy_bytes(): destination: abcd <-- expected
C:\20110211-gcc-bug>mingw32-gcc.exe -O example.c
-oexample.exe && example.exe
before copy_bytes(): source : abcd
before copy_bytes(): destination: 1234
calling copy_bytes(): copy source to destination
after copy_bytes(): source : abcd
after copy_bytes(): destination: 1234 <-- not expected: the bug in action
example.c:
#include
#include
typedef union PTR_UNION
{
char * as_s08_ptr;
unsigned int as_u32;
} PTR_UNION;
void copy_bytes(unsigned int address_as_u32, char * source, unsigned int size)
{
unsigned int i;
PTR_UNION destination;
destination.as_u32 = address_as_u32;
for (i=0 ; i= 1) && (destination.as_s08_ptr[0] != source[0])) {
exit(1);
}
#endif
}
void main(void)
{
PTR_UNION address;
char source[] = "abcd";
char destination[] = "1234";
printf("before copy_bytes(): source : %s\n", source);
printf("before copy_bytes(): destination: %s\n", destination);
printf("calling copy_bytes(): copy source to destination\n");
address.as_s08_ptr = destination;
copy_bytes(address.as_u32, source, sizeof(source));
printf("after copy_bytes(): source : %s\n", source);
printf("after copy_bytes(): destination: %s <-- %s\n", destination,
strcmp(source, destination) ? "not expected: the bug in action" : "expected");
}
Workaround:
If you find this bug but want to continue compiling your code with the -O
command line option then there are several workarounds:
1. Don't use the union :-)
2. Add the unnecessary code shown above.
