https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93249
Bug ID: 93249
Summary: [10 Regression] wrong code with __builtin_strncpy() at
-O1
Product: gcc
Version: 10.0
Status: UNCONFIRMED
Keywords: wrong-code
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: zsojka at seznam dot cz
Target Milestone: ---
Host: x86_64-pc-linux-gnu
Created attachment 47643
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=47643&action=edit
reduced testcase
Output:
$ x86_64-pc-linux-gnu-gcc -O testcase.c
$ ./a.out
Aborted
# testcase.c:6: char d[2] = { 0x00, 0x11 };
mov WORD PTR [rsp+14], 4352 # d,
# testcase.c:7: __builtin_strncpy (&b[2], d, 2);
mov edx, 1 #,
lea rsi, [rsp+15] # tmp102,
mov edi, OFFSET FLAT:b+3 #,
call strncpy #
The code copies b[3] = d[1] // == 0x11
It should have done:
b[2] = d[0] // later overwritten by the second strncpy
b[3] = 0 // strncpy zeroes all bytes in dest up to 'n'
$ x86_64-pc-linux-gnu-gcc -v
Using built-in specs.
COLLECT_GCC=/repo/gcc-trunk/binary-latest-amd64/bin/x86_64-pc-linux-gnu-gcc
COLLECT_LTO_WRAPPER=/repo/gcc-trunk/binary-trunk-280156-checking-yes-rtl-df-extra-amd64/bin/../libexec/gcc/x86_64-pc-linux-gnu/10.0.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: /repo/gcc-trunk//configure --enable-languages=c,c++
--enable-valgrind-annotations --disable-nls --enable-checking=yes,rtl,df,extra
--with-cloog --with-ppl --with-isl --build=x86_64-pc-linux-gnu
--host=x86_64-pc-linux-gnu --target=x86_64-pc-linux-gnu
--with-ld=/usr/bin/x86_64-pc-linux-gnu-ld
--with-as=/usr/bin/x86_64-pc-linux-gnu-as --disable-libstdcxx-pch
--prefix=/repo/gcc-trunk//binary-trunk-280156-checking-yes-rtl-df-extra-amd64
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 10.0.0 20200111 (experimental) (GCC)
The PR93213 patch doesn't seem to fix this issue.
