Hello Dave Rodgman,
The patch 50c4c616ec52: "lib/lzo: implement run-length encoding" from
Nov 30, 2018, leads to the following static checker warning:
lib/lzo/lzo1x_compress.c:164 lzo1x_1_do_compress()
error: uninitialized symbol 'm_pos'.
lib/lzo/lzo1x_compress.c
100 ir++;
101 run_length = ir - ip;
102 if (run_length > MAX_ZERO_RUN_LENGTH)
103 run_length = MAX_ZERO_RUN_LENGTH;
104 } else {
105 t = ((dv * 0x1824429d) >> (32 - D_BITS)) & D_MASK;
106 m_pos = in + dict[t];
^^^^^^^^^^^^^^^^^^^^^
We only initialize m_pos on the else path now.
107 dict[t] = (lzo_dict_t) (ip - in);
108 if (unlikely(dv != get_unaligned_le32(m_pos)))
109 goto literal;
110 }
111
112 ii -= ti;
113 ti = 0;
114 t = ip - ii;
115 if (t != 0) {
116 if (t <= 3) {
117 op[*state_offset] |= t;
118 COPY4(op, ii);
119 op += t;
120 } else if (t <= 16) {
121 *op++ = (t - 3);
122 COPY16(op, ii);
123 op += t;
124 } else {
125 if (t <= 18) {
126 *op++ = (t - 3);
127 } else {
128 size_t tt = t - 18;
129 *op++ = 0;
130 while (unlikely(tt > 255)) {
131 tt -= 255;
132 *op++ = 0;
133 }
134 *op++ = tt;
135 }
136 do {
137 COPY16(op, ii);
138 op += 16;
139 ii += 16;
140 t -= 16;
141 } while (t >= 16);
142 if (t > 0) do {
143 *op++ = *ii++;
144 } while (--t > 0);
145 }
146 }
147
148 if (unlikely(run_length)) {
149 ip += run_length;
150 run_length -= MIN_ZERO_RUN_LENGTH;
151 put_unaligned_le32((run_length << 21) | 0xfffc18
152 | (run_length & 0x7), op);
153 op += 4;
154 run_length = 0;
155 *state_offset = -3;
156 goto finished_writing_instruction;
157 }
158
159 m_len = 4;
160 {
161 #if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) && defined(LZO_USE_CTZ64)
162 u64 v;
163 v = get_unaligned((const u64 *) (ip + m_len)) ^
164 get_unaligned((const u64 *) (m_pos + m_len));
^^^^^^^^^^^^^
Smatch complains here.
165 if (unlikely(v == 0)) {
166 do {
167 m_len += 8;
168 v = get_unaligned((const u64 *) (ip + m_len)) ^
169 get_unaligned((const u64 *) (m_pos + m_len));
170 if (unlikely(ip + m_len >= ip_end))
171 goto m_len_done;
172 } while (v == 0);
173 }
regards,
dan carpenter
