gcc -pipe -static-libgcc -O3 -flto -march=native -o fdkaac.exe src/aacenc.o src/caf_reader.o src/extrapolater.o src/limiter.o src/lpc.o src/m4af.o src/main.o src/metadata.o src/parson.o src/pcm_float_converter.o src/pcm_native_converter.o src/pcm_readhelper.o src/pcm_sint16_converter.o src/progress.o src/wav_reader.o src/compat_win32.o fdkaac.o -liconv -lfdk-aac -lm -lfdk-aac
In function 'apple_chan_chunk',
inlined from 'caf_parse' at src/caf_reader.c:190:17,
inlined from 'caf_open' at src/caf_reader.c:230:9,
inlined from 'open_input' at src/main.c:754:27,
inlined from 'main' at src/main.c:802:19:
src/pcm_readhelper.c:231:24: warning: writing 1 byte into a region of size 0 [-Wstringop-overflow=]
231 | mapping[i] = i;
| ^
src/main.c: In function 'main':
src/caf_reader.c:29:13: note: at offset 0 to object 'chanmap' with size 8 declared here
29 | uint8_t chanmap[8];
| ^
Zero-lenght arrays are GNU C extension. There's ISO C99 flexible array member, which is preffered mechanism to declare variable-length types.
Flexible array member allows us to avoid applying sizeof operator cause it's incomplete type, so it will be an error at compile time. There're any moments else why it's better way to implement such structures via FAM:
https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
In this issue it fixed gcc 10 warning:
"warning: writing 1 byte into a region of size 0 [-Wstringop-overflow=]"
nkh0472
commented
3 years ago
There is a warning when compiling fdkaac 1.0.2 using the latest MinGW with MYSYS2.
Version info of GCC
``` $ gcc -v Using built-in specs. COLLECT_GCC=E:\Etc\HUGE\msys64\mingw64\bin\gcc.exe COLLECT_LTO_WRAPPER=E:/Etc/HUGE/msys64/mingw64/bin/../lib/gcc/x86_64-w64-mingw32/10.3.0/lto-wrapper.exe Target: x86_64-w64-mingw32 Configured with: ../gcc-10.3.0/configure --prefix=/mingw64 --with-local-prefix=/mingw64/local --build=x86_64-w64-mingw32 --host=x86_64-w64-mingw32 --target=x86_64-w64-mingw32 --with-native-system-header-dir=/mingw64/x86_64-w64-mingw32/include --libexecdir=/mingw64/lib --enable-bootstrap --enable-checking=release --with-arch=x86-64 --with-tune=generic --enable-languages=c,lto,c++,fortran,ada,objc,obj-c++,jit --enable-shared --enable-static --enable-libatomic --enable-threads=posix --enable-graphite --enable-fully-dynamic-string --enable-libstdcxx-filesystem-ts=yes --enable-libstdcxx-time=yes --disable-libstdcxx-pch --disable-libstdcxx-debug --enable-lto --enable-libgomp --disable-multilib --disable-rpath --disable-win32-registry --disable-nls --disable-werror --disable-symvers --with-libiconv --with-system-zlib --with-gmp=/mingw64 --with-mpfr=/mingw64 --with-mpc=/mingw64 --with-isl=/mingw64 --with-pkgversion='Rev2, Built by MSYS2 project' --with-bugurl=https://github.com/msys2/MINGW-packages/issues --with-gnu-as --with-gnu-ld --with-boot-ldflags='-pipe -Wl,--dynamicbase,--high-entropy-va,--nxcompat,--default-image-base-high -Wl,--disable-dynamicbase -static-libstdc++ -static-libgcc' 'LDFLAGS_FOR_TARGET=-pipe -Wl,--dynamicbase,--high-entropy-va,--nxcompat,--default-image-base-high' --enable-linker-plugin-flags='LDFLAGS=-static-libstdc++\ -static-libgcc\ -pipe\ -Wl,--dynamicbase,--high-entropy-va,--nxcompat,--default-image-base-high\ -Wl,--stack,12582912' Thread model: posix Supported LTO compression algorithms: zlib zstd gcc version 10.3.0 (Rev2, Built by MSYS2 project) ```The compile script is basically as follows:
During compiling, there is a warning as (full logs in https://github.com/kekyo/fdk-aac-win32-builder/issues/9#issuecomment-852979506)
According to a similar problem in another project (https://github.com/tarantool/tarantool/issues/5564), this warning is due to a zero-lenght array when
i=0: https://github.com/nu774/fdkaac/blob/347e995cfc44941f6d6dfe8d4e09362a71ea8d26/src/pcm_readhelper.c#L230-L231Thus, this commit will use variable array explicitly to avoid this GCC warning.
The info below is cited from https://github.com/tarantool/tarantool/commit/8915ae203f873198caf76fbad4bf9edce76a6153