https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109789
Bug ID: 109789
Summary: analyzer-use-of-uninitialized-value false positive
Product: gcc
Version: 13.1.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: alex at zrythm dot org
Target Milestone: ---
Created attachment 55028
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=55028&action=edit
gcc invocation output showing the error
The first error in the attached gcc output is a false positive because the
`tmp_l` float array is initialized for its whole size right after it is
declared, and the same size is passed to the function where the error occurs.
That function loops over the float array and calls `fabsf` causing this
analyzer error.
This is essentially the code:
```c
float tmp_l[nframes]; // this is the array
for (nframes_t i = 0; i < nframes; i++)
{
tmp_l[i] = P_MASTER_TRACK->channel->stereo_out->l->buf[i];
}
float max_amp = dsp_abs_max (tmp_l, nframes); // this is the function called
```
The function code:
```c
static inline float
dsp_abs_max (float * buf, size_t size)
{
float ret = 1e-20f;
for (size_t i = 0; i < size; i++)
{
if (fabsf (buf[i]) > ret)
{
ret = fabsf (buf[i]);
}
}
return ret;
```
As you can see, `tmp_l` is initialized for its whole size, which is then passed
to the function above to loop over it, so the analyzer saying the value is
uninitialized is wrong.
Below is the gcc invocation command used:
```
LANG=C gcc -v -save-temps -Isrc/libzrythm-lib.so.p -Isrc -I../src -I. -I..
-Iinc -I../inc -Iext -I../ext -Iext/kissfft -I../ext/kissfft -Iext/midilib
-I../ext/midilib -Iext/whereami -I../ext/whereami -Iext/weakjack
-I../ext/weakjack -I../inc/plugins/lv2 -Isubprojects/libadwaita/src
-I../subprojects/libadwaita/src -Isubprojects/gtk4 -I../subprojects/gtk4
-Isubprojects/gtk4/gtk -I../subprojects/gtk4/gtk -Isubprojects/pango-1.50.6
-I../subprojects/pango-1.50.6 -Isubprojects/pango-1.50.6/pango
-I../subprojects/pango-1.50.6/pango -Isubprojects/gtk4/gdk/x11
-I../subprojects/gtk4/gdk/x11 -Isubprojects/gtk4/gdk -I../subprojects/gtk4/gdk
-Isubprojects/libpanel/src -I../subprojects/libpanel/src -Isubprojects/libpanel
-I../subprojects/libpanel -Isubprojects/libsndfile-1.1.0
-I../subprojects/libsndfile-1.1.0 -I../subprojects/libsndfile-1.1.0/src
-I../subprojects/libcyaml/include -Isubprojects/libaudec
-I../subprojects/libaudec -Isubprojects/libaudec/inc
-I../subprojects/libaudec/inc -Isubprojects/rtaudio -I../subprojects/rtaudio
-I../subprojects/rtmidi/rtmidi -I../subprojects/zstd-1.4.5/lib
-I../subprojects/zstd-1.4.5/lib/common -I../subprojects/zstd-1.4.5/lib/compress
-I../subprojects/zstd-1.4.5/lib/decompress
-I../subprojects/zstd-1.4.5/lib/dictBuilder
-I../subprojects/zstd-1.4.5/lib/deprecated
-I../subprojects/zstd-1.4.5/lib/legacy -I../subprojects/reproc/reproc/include
-Isubprojects/reproc/__CMake_build -I../subprojects/reproc/__CMake_build
-Isubprojects/reproc -I../subprojects/reproc -Isubprojects/pcre-8.37
-I../subprojects/pcre-8.37 -Isubprojects/pcre2-10.39
-I../subprojects/pcre2-10.39 -I../subprojects/pcre2-10.39/src
-Isubprojects/xxHash-0.8.0 -I../subprojects/xxHash-0.8.0
-Isubprojects/json-glib -I../subprojects/json-glib -I../subprojects/zix/include
-Isubprojects/gtk4/gtk/css -Isubprojects/gtk4/gsk -Isubprojects/libbacktrace
-Isubprojects/json-glib/json-glib -I/usr/include/glib-2.0
-I/usr/lib/glib-2.0/include -I/usr/include/sysprof-4 -I/home/alex/local/include
-I/usr/include/libmount -I/usr/include/blkid -I/usr/include/gio-unix-2.0
-I/usr/include/fribidi -I/usr/include/harfbuzz -I/usr/include/freetype2
-I/usr/include/libpng16 -I/usr/include/cairo -I/usr/include/pixman-1
-I/usr/include/gdk-pixbuf-2.0 -I/usr/include/graphene-1.0
-I/usr/lib/graphene-1.0/include -I/usr/include/lzo -I/usr/include/graphviz
-I/usr/include/guile/3.0 -I/usr -I/usr/include/carla
-I/usr/include/carla/includes -I/usr/include/serd-0 -I/usr/include/sord-0
-I/usr/include/sratom-0 -I/usr/include/lilv-0 -I/usr/include/gtksourceview-5
-I/home/alex/local/include/gtk-4.0 -I/home/alex/local/include/pango-1.0
-I/usr/include/libxml2 -I/usr/include/valgrind
-I/home/alex/Documents/git/zrythm/build/subprojects/libbacktrace/dist/home/alex/local/include
-I/usr/include/dbus-1.0 -I/usr/lib/dbus-1.0/include -fdiagnostics-color=always
-D_FILE_OFFSET_BITS=64 -Wall -Winvalid-pch -Wextra -std=gnu11 -O0 -g
-DGLIB_VERSION_MIN_REQUIRED=GLIB_VERSION_2_70
-DGLIB_VERSION_MAX_ALLOWED=GLIB_VERSION_2_70
-DGDK_VERSION_MIN_REQUIRED=GDK_VERSION_4_8
-DGDK_VERSION_MAX_ALLOWED=GDK_VERSION_4_8 -Wno-bad-function-cast
-Wno-old-style-declaration -Werror=absolute-value -Wformat=2
-Wno-missing-field-initializers -Wno-unused-parameter -Wno-sequence-point
-Wignored-qualifiers -Wno-cast-function-type -Walloca -fno-common
-frecord-gcc-switches -march=native -mtune=native -ffast-math -fstrength-reduce
-fdata-sections -ffunction-sections -freciprocal-math
-fsingle-precision-constant -msse -msse2 -mfpmath=sse -fno-math-errno
-fno-omit-frame-pointer -g3 -rdynamic -funwind-tables
-fasynchronous-unwind-tables -fno-toplevel-reorder '-DGETTEXT_PACKAGE="zrythm"'
-fPIC -DZIX_STATIC -DXXH_INLINE_HINTS -DXXH_STATIC_LINKING_ONLY -mfpmath=sse
-msse -msse2 -pthread -DREAL_BUILD -D_REENTRANT
-isystem/usr/include/graphene-1.0 -isystem/usr/lib/graphene-1.0/include
-mfpmath=sse -msse -msse2 -isystem/usr/include/glib-2.0
-isystem/usr/lib/glib-2.0/include -isystem/usr/include/sysprof-4
-isystem/home/alex/local/include -mfpmath=sse -msse -msse2 -Wformat=2
-Wno-missing-field-initializers -Wno-unused-parameter -Wno-sequence-point
-Wignored-qualifiers -Wno-cast-function-type -Walloca -fno-common
'-DLV2_UI__Gtk4UI="https://lv2plug.in/ns/extensions/ui#Gtk4UI";' '-D__(x)=x'
-DG_LOG_USE_STRUCTURED=1 '-DG_LOG_DOMAIN="zrythm"' -DREALTIME=
'-DDEPRECATED_MSG(x)=__attribute__((deprecated(x)))'
'-DOPTIMIZE(x)=__attribute__((optimize(#x)))' '-DOPTIMIZE_O0=OPTIMIZE(O0)'
'-DOPTIMIZE_O1=OPTIMIZE(O1)' '-DOPTIMIZE_O2=OPTIMIZE(O2)'
'-DOPTIMIZE_O3=OPTIMIZE(O3)' '-DNOINLINE=__attribute__((noinline))'
'-DNONNULL_ARGS(...)=__attribute__((nonnull(__VA_ARGS__)))'
'-DACCESS(...)=__attribute__((access(__VA_ARGS__)))'
'-DACCESS_READ_ONLY(...)=ACCESS(read_only,__VA_ARGS__)' -frecord-gcc-switches
'-DALWAYS_INLINE=__attribute__((always_inline))' '-DCOLD=__attribute__((cold))'
'-DHOT=__attribute__((hot))' '-DPURE=__attribute__((pure))'
'-DNONNULL=__attribute__((nonnull))'
'-DRETURNS_NONNULL=__attribute__((returns_nonnull))'
'-DSTACK_PROTECT=__attribute__((stack_protect))'
'-DNO_STACK_PROTECTOR=__attribute__((no_stack_protector))'
'-DWARN_UNUSED_RESULT=__attribute__((warn_unused_result))'
'-DCONST=__attribute__((const))' '-DMALLOC=__attribute__((malloc))'
-march=native -mtune=native -ffast-math -fstrength-reduce -DPIC -fdata-sections
-ffunction-sections -freciprocal-math -fsingle-precision-constant -msse -msse2
-mfpmath=sse -fno-math-errno -fno-omit-frame-pointer -g3 -rdynamic
-funwind-tables -fasynchronous-unwind-tables -fno-toplevel-reorder
-Werror=format-overflow -Werror=format-truncation -Werror=clobbered
-Werror=disabled-optimization -Werror=float-equal -Werror=logical-op
-Werror=pointer-arith -Werror=enum-conversion -Werror=overlength-strings
-Werror=stringop-truncation -Werror=missing-declarations
-Werror=int-to-pointer-cast -Werror=shadow -Werror=undef -Werror=unused
-fstrict-aliasing -Wstrict-aliasing=2 -Werror=strict-aliasing
-Wstrict-overflow=2 -fstrict-overflow -Werror=duplicated-branches
-Werror=duplicated-cond -Werror=null-dereference -Werror=init-self
-Werror=jump-misses-init -Werror=missing-prototypes -Werror=nested-externs
-Werror=write-strings -Werror=sign-compare -Werror=discarded-qualifiers
-Werror=float-conversion -Werror=implicit-function-declaration
-Werror=uninitialized -Werror=maybe-uninitialized -Werror=return-type
-Werror=int-conversion -Werror=incompatible-pointer-types -Werror=implicit-int
-Werror=multistatement-macros -Werror=switch -Werror=overflow
-Werror=array-bounds -Werror=enum-compare -Werror=misleading-indentation
-Werror=int-in-bool-context -Werror=type-limits -Werror=deprecated-declarations
-Werror=endif-labels -Werror=logical-not-parentheses -Werror=parentheses
-Werror=comment -Werror=sizeof-pointer-div -Werror=shift-count-overflow
-Werror=free-nonheap-object -fanalyzer
-Werror=analyzer-possible-null-dereference -Werror=analyzer-malloc-leak
-Werror=analyzer-null-dereference -Werror=analyzer-null-argument
-Werror=analyzer-use-after-free -Werror=analyzer-possible-null-argument
-Werror=analyzer-double-free -Werror=analyzer-file-leak
-Werror=analyzer-use-of-uninitialized-value -Werror=analyzer-out-of-bounds
-Werror=nonnull -Werror=nonnull-compare -Werror=override-init
-Werror=bool-compare -Werror=tautological-compare -Werror=unused-result
-Werror=inline -Werror=duplicate-decl-specifier -Werror=redundant-decls
-Werror=strict-prototypes -Werror=sizeof-array-argument
-Werror=lto-type-mismatch -Werror=odr -Wsuggest-attribute=pure
-Wsuggest-attribute=const -Wsuggest-attribute=noreturn
-Wsuggest-attribute=format -Wsuggest-attribute=malloc -Wsuggest-attribute=cold
-Werror=sign-conversion -Werror=implicit-fallthrough -Werror=format=2 -MD -MQ
src/libzrythm-lib.so.p/audio_exporter.c.o -MF
src/libzrythm-lib.so.p/audio_exporter.c.o.d -o
src/libzrythm-lib.so.p/audio_exporter.c.o -c ../src/audio/exporter.c
```
