Code matches with addition inside `strlen` for the top ~100 GH repos. Searched for `strlen(:[x]+:[[y]])` and `strlen(:[x] + :[[y]])` with comby.

all-inside-strlen.txt

FFmpeg.git-2019-09-30-23-45-37/libavcodec/h264_metadata_bsf.c:strlen(ctx->sei_user_data + i + 1)
FFmpeg.git-2019-09-30-23-45-37/libavformat/ffmetadec.c:strlen(p + 1)
FFmpeg.git-2019-09-30-23-45-37/libavformat/libopenmpt.c:strlen(ext + 1)
curl.git-2019-09-30-23-46-33/lib/vtls/vtls.c:strlen(begin_pos + 8)
curl.git-2019-09-30-23-46-33/lib/socks.c:strlen((char *)socksreq + 8)
curl.git-2019-09-30-23-46-33/tests/server/getpart.c:strlen(*buffer + offset)
fastdfs.git-2019-10-01-00-16-06/client/client_func.c:strlen(fileExtName + 1)
git.git-2019-09-30-23-45-09/config.c:strlen(key + store->baselen + 1)
git.git-2019-09-30-23-45-09/connect.c:strlen(for_pos + 5)
git.git-2019-09-30-23-45-09/sha1-name.c:strlen(real_ref + 11)
git.git-2019-09-30-23-45-09/remote.c:strlen(kstar + 1)
h2o.git-2019-09-30-23-58-50/deps/picohttpparser/test.c:strlen(buf + bytes_ready)
h2o.git-2019-09-30-23-58-50/lib/handler/configurator/headers_util.c:strlen(colon + 1)
lab.git-2019-10-01-00-06-50/engine/code/game/ai_dmq3.c:strlen(ptr + 1)
libgit2.git-2019-10-01-00-00-52/src/refspec.c:strlen(name + star_offset)
libgit2.git-2019-10-01-00-00-52/src/refspec.c:strlen(from_star + 1)
libgit2.git-2019-10-01-00-00-52/src/index.c:strlen(path_ptr + varint_len)
libuv.git-2019-09-30-23-48-55/test/test-fs.c:strlen(test_dir + 4)
lwan.git-2019-10-01-00-24-37/src/lib/patterns.c:strlen(p + upto)
macvim.git-2019-10-01-00-17-11/runtime/tools/xcmdsrv_client.c:strlen(property + length + 1)
masscan.git-2019-09-30-23-52-58/src/output.c:strlen(filename + x_off)
mjolnir.git-2019-10-01-00-24-08/Mjolnir/lua/lstrlib.c:strlen(p + upto)
mjolnir.git-2019-10-01-00-24-08/Mjolnir/lua/lstrlib.c:strlen(data + pos)
openssl.git-2019-09-30-23-49-57/crypto/x509/v3_pci.c:strlen(val->value + 5)
php-src.git-2019-09-30-23-45-09/ext/openssl/xp_ssl.c:strlen(wildcard + 1)
php-src.git-2019-09-30-23-45-09/ext/standard/php_fopen_wrapper.c:strlen(path + 6)
php-src.git-2019-09-30-23-45-09/ext/pdo/pdo_dbh.c:strlen(colon + 1)
php-src.git-2019-09-30-23-45-09/ext/phar/phar_object.c:strlen(u + 1)
radare2.git-2019-09-30-23-50-36/libr/asm/arch/msp430/msp430_disas.c:strlen(strchr(cmd->operands, ',') + 2)
reactos.git-2019-10-01-00-01-08/modules/rostests/apitests/crt/strlen.c:strlen(teststr + 4)
reactos.git-2019-10-01-00-01-08/base/setup/usetup/cmdcons.c:strlen(str + current)
reactos.git-2019-10-01-00-01-08/base/applications/winhlp32/macro.c:strlen(ptr + 1)
reactos.git-2019-10-01-00-01-08/modules/rostests/winetests/shell32/shlexec.c:strlen(tmplongpath + lp)
reactos.git-2019-10-01-00-01-08/modules/rosapps/applications/cmdutils/touch/touch.c:strlen(p + 1)
reactos.git-2019-10-01-00-01-08/modules/rosapps/applications/net/tsclient/rdesktop/rdesktop.c:strlen(optarg + 11)
reactos.git-2019-10-01-00-01-08/modules/rostests/winetests/gdi32/dc.c:strlen(buf + 2)
reactos.git-2019-10-01-00-01-08/modules/rostests/winetests/gdi32/dc.c:strlen(buf + 2)
reactos.git-2019-10-01-00-01-08/modules/rosapps/applications/net/ncftp/libncftp/open.c:strlen(lastslash + 1)
reactos.git-2019-10-01-00-01-08/modules/rosapps/applications/net/ncftp/libncftp/glob.c:strlen(cp + 1)
reactos.git-2019-10-01-00-01-08/modules/rosapps/applications/net/ncftp/ncftp/getline.c:strlen(cp + 1)
reactos.git-2019-10-01-00-01-08/modules/rosapps/applications/net/ncftp/ncftp/getline.c:strlen(cp + 1)
reactos.git-2019-10-01-00-01-08/modules/rosapps/applications/net/ncftp/ncftp/bookmark.c:strlen(bmp->pass + kPasswordMagicLen)
reactos.git-2019-10-01-00-01-08/modules/rosapps/applications/net/ncftp/ncftp/util.c:strlen(a + 3)
reactos.git-2019-10-01-00-01-08/modules/rosapps/applications/net/ncftp/ncftp/util.c:strlen(a + 3)
reactos.git-2019-10-01-00-01-08/modules/rosapps/applications/net/ncftp/ncftp/util.c:strlen(dst + 1)
reactos.git-2019-10-01-00-01-08/win32ss/gdi/gdi32/wine/enhmfdrv/init.c:strlen(description + len1 + 1)
reactos.git-2019-10-01-00-01-08/dll/win32/shlwapi/reg.c:strlen(lpExt + 1)
reactos.git-2019-10-01-00-01-08/dll/win32/inetcomm/mimeole.c:strlen(cp + 1)
reactos.git-2019-10-01-00-01-08/sdk/tools/rsym/rsym.c:strlen(LineInfo->FileName + i + 1)
reactos.git-2019-10-01-00-01-08/sdk/tools/mkisofs/schilytools/mkisofs/tree.c:strlen(table->table + count)
skynet.git-2019-09-30-23-59-50/3rd/lua/lstrlib.c:strlen(p + upto)
skynet.git-2019-09-30-23-59-50/3rd/lua/lstrlib.c:strlen(data + pos)
sway.git-2019-10-01-00-01-56/sway/config.c:strlen(find + 1)
sway.git-2019-10-01-00-01-56/swaybar/status_line.c:strlen(newline + 1)
systemd.git-2019-10-01-00-13-42/src/test/test-socket-util.c:strlen(abstract.sun_path + 1)
systemd.git-2019-10-01-00-13-42/src/libsystemd/sd-hwdb/sd-hwdb.c:strlen(prefix + p)
tig.git-2019-10-01-00-00-00/src/refdb.c:strlen(sep + 1)
tig.git-2019-10-01-00-00-00/src/options.c:strlen(arg + 1)
tig.git-2019-10-01-00-00-00/src/prompt.c:strlen(search + 1)
tig.git-2019-10-01-00-00-00/src/diff.c:strlen(context + len)
tig.git-2019-10-01-00-00-00/compat/wordexp.c:strlen(words + 1)
toxcore.git-2019-09-30-23-59-09/testing/nTox.c:strlen(*posi + 1)
toxcore.git-2019-09-30-23-59-09/testing/nTox.c:strlen(*posi + 1)
vlc.git-2019-10-01-00-14-59/modules/access/dsm/access.c:strlen(iter + 1)
vlc.git-2019-10-01-00-14-59/modules/access/satip.c:strlen(tok + 12)
vlc.git-2019-10-01-00-14-59/modules/access/satip.c:strlen(tok + 5)
vlc.git-2019-10-01-00-14-59/modules/access/http/hpack.c:strlen(dec->table[evicted] + namelen + 1)
FFmpeg.git-2019-09-30-23-45-37/libavformat/wavenc.c:strlen(tmp_tag->value+2)
curl.git-2019-09-30-23-46-33/src/tool_operhlp.c:strlen(++ptr)
disque.git-2019-10-01-00-00-44/src/disque-cli.c:strlen(buf+startpos)
fastdfs.git-2019-10-01-00-16-06/tracker/tracker_proto.c:strlen(pSeperator+1)
git.git-2019-09-30-23-45-09/dir.c:strlen(++pattern)
git.git-2019-09-30-23-45-09/refspec.c:strlen(++rhs)
git.git-2019-09-30-23-45-09/transport.c:strlen(++anon_part)
lab.git-2019-10-01-00-06-50/engine/code/q3_ui/ui_playermodel.c:strlen(pdest+5)
lab.git-2019-10-01-00-06-50/engine/code/q3_ui/ui_playermodel.c:strlen(pdest+5)
lab.git-2019-10-01-00-06-50/engine/code/game/ai_dmq3.c:strlen(ptr+1)
lab.git-2019-10-01-00-06-50/engine/code/game/ai_dmq3.c:strlen(str2+1)
lab.git-2019-10-01-00-06-50/engine/code/game/ai_dmq3.c:strlen(str1+1)
lab.git-2019-10-01-00-06-50/engine/code/game/ai_dmq3.c:strlen(name+2)
lab.git-2019-10-01-00-06-50/engine/code/botlib/l_precomp.c:strlen(newtoken.string+1)
libgit2.git-2019-10-01-00-00-52/src/refspec.c:strlen(++rhs)
masscan.git-2019-09-30-23-52-58/src/rawsock-pcapfile.c:strlen(capfilename+i)
masscan.git-2019-09-30-23-52-58/src/templ-payloads.c:strlen(line+5)
openssl.git-2019-09-30-23-49-57/test/evp_test.c:strlen(++value)
php-src.git-2019-09-30-23-45-09/ext/bcmath/bcmath.c:strlen(p+1)
reactos.git-2019-10-01-00-01-08/modules/rostests/winetests/shlwapi/url.c:strlen(test->url+test->protocol_len+1)
reactos.git-2019-10-01-00-01-08/modules/rostests/winetests/shlwapi/url.c:strlen(test->url+test->protocol_len+1)
reactos.git-2019-10-01-00-01-08/dll/win32/version/version.c:strlen(tmpfn+tmplast)
reactos.git-2019-10-01-00-01-08/dll/win32/version/version.c:strlen(tmpfn+tmplast)
reactos.git-2019-10-01-00-01-08/dll/3rdparty/libjpeg/wrjpgcom.c:strlen(argv[argn]+1)
reactos.git-2019-10-01-00-01-08/sdk/lib/crt/locale/locale.c:strlen(buf+len)
redis-3.0-annotated.git-2019-10-01-00-14-46/src/redis-cli.c:strlen(buf+startpos)
redis-3.0-annotated.git-2019-10-01-00-14-46/src/rdb.c:strlen((char*)buf+1)
redis.git-2019-09-30-23-45-09/src/redis-cli.c:strlen(buf+startpos)
redis.git-2019-09-30-23-45-09/src/redis-cli.c:strlen(buf+5)
redis.git-2019-09-30-23-45-09/src/replication.c:strlen(buf+5)
redis.git-2019-09-30-23-45-09/src/bitops.c:strlen(p+1)
redis.git-2019-09-30-23-45-09/src/config.c:strlen(p+5)
redis.git-2019-09-30-23-45-09/src/rdb.c:strlen((char*)buf+1)
systemd.git-2019-10-01-00-13-42/src/basic/socket-util.c:strlen(s+1)
systemd.git-2019-10-01-00-13-42/src/libsystemd/sd-hwdb/hwdb-util.c:strlen(search + i+1)
torch7.git-2019-09-30-23-59-42/lib/TH/THDiskFile.c:strlen(p+pos)
vlc.git-2019-10-01-00-14-59/src/input/item.c:strlen(++ext)
winfile.git-2019-10-01-00-13-26/src/wfdlgs2.c:strlen(pszXlate+cchOffset)