[Bug c/87344] New: archival/libarchive/decompress_gunzip.c:1139:2: error: size of unnamed array is negative

[yellowriver2010 at hotmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87344

            Bug ID: 87344
           Summary: archival/libarchive/decompress_gunzip.c:1139:2: error:
                    size of unnamed array is negative
           Product: gcc
           Version: 6.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: yellowriver2010 at hotmail dot com
  Target Milestone: ---

Created attachment 44710
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=44710&action=edit
compile.sh

# ./compile.sh
archival/libarchive/decompress_gunzip.c:1:0: warning: this target machine does
not have delayed branches [enabled by default]
archival/libarchive/decompress_gunzip.c:1:0: warning: -fassociative-math
disabled; other options take precedence [enabled by default]
archival/libarchive/decompress_gunzip.c: In function ‘check_header_gzip’:
archival/libarchive/decompress_gunzip.c:1139:2: error: size of unnamed array is
negative





The orignal code is:
1126 static int check_header_gzip(STATE_PARAM transformer_state_t *xstate)
1127 {
1128     union {
1129         unsigned char raw[8];
1130         struct {
1131             uint8_t gz_method;
1132             uint8_t flags;
1133             uint32_t mtime;
1134             uint8_t xtra_flags_UNUSED;
1135             uint8_t os_flags_UNUSED;
1136         } PACKED formatted;
1137     } header;
1138
1139     BUILD_BUG_ON(sizeof(header) != 8);


The preprocessed code is:
11347 static int check_header_gzip(state_t *state, transformer_state_t *xstate)
11348 {
11349  union {
11350   unsigned char raw[8];
11351   struct {
11352    uint8_t gz_method;
11353    uint8_t flags;
11354    uint32_t mtime;
11355    uint8_t xtra_flags_UNUSED;
11356    uint8_t os_flags_UNUSED;
11357   } __attribute__ ((__packed__)) formatted;
11358  } header;
11359
11360  ((void)sizeof(char[1 - 2*!!(sizeof(header) != 8)]));