Nasty typecasting / alignment issues in libdvbpsi

Dear livdvbpsi developers,

When compiling for host=mipsel-linux-uclibc (mipsel-linux-uclibc-gcc
(GCC) 4.2.0), I ran into some rather horrible alignment issues related
to typecasting of the various table structures.

I got the following warnings (which become errors due to -Werror)
using the latest git as of today
(398ff6bac45aeda35320ff1b7535e726290af821)

libtool: compile:  mipsel-linux-uclibc-gcc -DHAVE_CONFIG_H -I. -I.. -g
-O2 -Wall -Werror --std=gnu99 -D_GNU_SOURCE -Wpointer-arith
-Wcast-align -Wcast-qual -Wstrict-prototypes -Wshadow
-Waggregate-return -Wmissing-prototypes -Wnested-externs
-Wsign-compare -DDVBPSI_DIST -MT tot.lo -MD -MP -MF .deps/tot.Tpo -c
tables/tot.c  -fPIC -DPIC -o .libs/tot.o
cc1: warnings being treated as errors
tables/tot.c: In function 'dvbpsi_tot_attach':
tables/tot.c:78: warning: cast increases required alignment of target type
tables/tot.c: In function 'dvbpsi_tot_detach':
tables/tot.c:131: warning: cast increases required alignment of target type
tables/tot.c: In function 'dvbpsi_tot_sections_gather':
tables/tot.c:326: warning: cast increases required alignment of target type


For example, in src/tables/tot.c:78
    dvbpsi_tot_decoder_t *p_tot_decoder;
    p_tot_decoder = (dvbpsi_tot_decoder_t *) dvbpsi_decoder_new(NULL,
                                                0, true,
sizeof(dvbpsi_tot_decoder_t));

So apparently, p_tot_decoder potentially has a different alignment to
the result of dvbpsi_decoder_new. I imagine that this could lead to a
crash in libdvbpsi if the warning is ignored. Also, a separate issue:
the libdvbpsi library appears not to compile without -Werror either
for my mips toolchain or the regular centOS x86_64 toolchain, though I
didn't have time to investigate.

Best regards,

Martin Jackson


I got it compiling with the following hacks: (no suggestion that this
patch should be merged, it's nonsense but it got the job done for now)

diff --git a/src/demux.h b/src/demux.h
index 73b4ae0..c348153 100644
--- a/src/demux.h
+++ b/src/demux.h
@@ -126,7 +126,7 @@ struct dvbpsi_demux_s
     dvbpsi_demux_new_cb_t     pf_new_callback;    /*!< New subtable callback */
     void *                    p_new_cb_data;      /*!< Data provided to the
                                                      previous callback */
-};
+} __attribute__((__aligned__(128)));

 /*****************************************************************************
  * dvbpsi_AttachDemux
@@ -211,7 +211,7 @@ typedef void (* dvbpsi_callback_gather_t)(dvbpsi_t
*p_dvbpsi,  /*!< pointer to d
 struct dvbpsi_decoder_s
 {
     DVBPSI_DECODER_COMMON
-};
+} __attribute__((__aligned__(128)));

 /*****************************************************************************
  * dvbpsi_decoder_new
diff --git a/src/tables/atsc_eit.h b/src/tables/atsc_eit.h
index 82f72d6..94bb5da 100644
--- a/src/tables/atsc_eit.h
+++ b/src/tables/atsc_eit.h
@@ -83,7 +83,7 @@ typedef struct dvbpsi_atsc_eit_s
     dvbpsi_atsc_eit_event_t   *p_first_event;   /*!< First event
information structure. */

     dvbpsi_descriptor_t     *p_first_descriptor; /*!< First
descriptor structure. */
-} dvbpsi_atsc_eit_t;
+} __attribute__((__aligned__(128))) dvbpsi_atsc_eit_t;

 /*****************************************************************************
  * dvbpsi_eit_callback
diff --git a/src/tables/atsc_ett.h b/src/tables/atsc_ett.h
index 6baaf61..4f6eb76 100644
--- a/src/tables/atsc_ett.h
+++ b/src/tables/atsc_ett.h
@@ -70,7 +70,7 @@ typedef struct dvbpsi_atsc_ett_s
                                                  multiple string structure */

     dvbpsi_descriptor_t    *p_first_descriptor; /*!< First descriptor. */
-} dvbpsi_atsc_ett_t;
+} __attribute__((__aligned__(128)))  dvbpsi_atsc_ett_t;

 /*****************************************************************************
  * dvbpsi_atsc_ett_callback
diff --git a/src/tables/atsc_mgt.h b/src/tables/atsc_mgt.h
index d55fdad..004c44a 100644
--- a/src/tables/atsc_mgt.h
+++ b/src/tables/atsc_mgt.h
@@ -83,7 +83,7 @@ typedef struct dvbpsi_atsc_mgt_s
     dvbpsi_atsc_mgt_table_t   *p_first_table;   /*!< First table
information structure. */

     dvbpsi_descriptor_t    *p_first_descriptor; /*!< First descriptor. */
-} dvbpsi_atsc_mgt_t;
+} __attribute__((__aligned__(128))) dvbpsi_atsc_mgt_t;

 /*****************************************************************************
  * dvbpsi_mgt_callback
diff --git a/src/tables/atsc_stt.h b/src/tables/atsc_stt.h
index eca622c..de620c4 100644
--- a/src/tables/atsc_stt.h
+++ b/src/tables/atsc_stt.h
@@ -55,7 +55,7 @@ typedef struct dvbpsi_atsc_stt_s
     uint16_t                i_daylight_savings; /*!< Daylight savings
control bytes. */

     dvbpsi_descriptor_t    *p_first_descriptor; /*!< First descriptor. */
-} dvbpsi_atsc_stt_t;
+} __attribute__((__aligned__(128)))  dvbpsi_atsc_stt_t;

 /*****************************************************************************
  * dvbpsi_atsc_stt_callback
diff --git a/src/tables/atsc_vct.h b/src/tables/atsc_vct.h
index cfe7e9e..7c395c8 100644
--- a/src/tables/atsc_vct.h
+++ b/src/tables/atsc_vct.h
@@ -97,7 +97,7 @@ typedef struct dvbpsi_atsc_vct_s
     dvbpsi_descriptor_t         *p_first_descriptor; /*!< First descriptor. */
     dvbpsi_atsc_vct_channel_t   *p_first_channel;    /*!< First
channel information structure. */

-} dvbpsi_atsc_vct_t;
+} __attribute__((__aligned__(128))) dvbpsi_atsc_vct_t;

 /*****************************************************************************
  * dvbpsi_vct_callback
diff --git a/src/tables/bat_private.h b/src/tables/bat_private.h
index ac6f726..5414902 100644
--- a/src/tables/bat_private.h
+++ b/src/tables/bat_private.h
@@ -44,7 +44,7 @@ typedef struct dvbpsi_bat_decoder_s
     dvbpsi_bat_t                  current_bat;
     dvbpsi_bat_t *                p_building_bat;

-} dvbpsi_bat_decoder_t;
+} __attribute__((__aligned__(128))) dvbpsi_bat_decoder_t;

 /*****************************************************************************
  * dvbpsi_bat_sections_gather
diff --git a/src/tables/cat_private.h b/src/tables/cat_private.h
index 93b862c..3269e49 100644
--- a/src/tables/cat_private.h
+++ b/src/tables/cat_private.h
@@ -45,7 +45,7 @@ typedef struct dvbpsi_cat_decoder_s
     dvbpsi_cat_t                  current_cat;
     dvbpsi_cat_t *                p_building_cat;

-} dvbpsi_cat_decoder_t;
+} __attribute__((__aligned__(128))) dvbpsi_cat_decoder_t;

 /*****************************************************************************
  * dvbpsi_cat_sections_gather
diff --git a/src/tables/eit_private.h b/src/tables/eit_private.h
index 1bf9108..8af52ea 100644
--- a/src/tables/eit_private.h
+++ b/src/tables/eit_private.h
@@ -45,7 +45,7 @@ typedef struct dvbpsi_eit_decoder_s

     uint8_t                       i_first_received_section_number;

-} dvbpsi_eit_decoder_t;
+} __attribute__((__aligned__(128))) dvbpsi_eit_decoder_t;

 /*****************************************************************************
  * dvbpsi_eit_sections_gather
diff --git a/src/tables/nit_private.h b/src/tables/nit_private.h
index 8eadce7..d1ccc8c 100644
--- a/src/tables/nit_private.h
+++ b/src/tables/nit_private.h
@@ -47,7 +47,7 @@ typedef struct dvbpsi_nit_decoder_s
     dvbpsi_nit_t                  current_nit;
     dvbpsi_nit_t *                p_building_nit;

-} dvbpsi_nit_decoder_t;
+} __attribute__((__aligned__(128))) dvbpsi_nit_decoder_t;

 /*****************************************************************************
  * dvbpsi_nit_sections_gather
diff --git a/src/tables/pat_private.h b/src/tables/pat_private.h
index 8801b0d..188e38b 100644
--- a/src/tables/pat_private.h
+++ b/src/tables/pat_private.h
@@ -43,7 +43,7 @@ typedef struct dvbpsi_pat_decoder_s
     dvbpsi_pat_t                  current_pat;
     dvbpsi_pat_t *                p_building_pat;

-} dvbpsi_pat_decoder_t;
+} __attribute__((__aligned__(128))) dvbpsi_pat_decoder_t;

 /*****************************************************************************
  * dvbpsi_pat_sections_gather
diff --git a/src/tables/pmt_private.h b/src/tables/pmt_private.h
index ed75a8b..2b936bd 100644
--- a/src/tables/pmt_private.h
+++ b/src/tables/pmt_private.h
@@ -45,7 +45,7 @@ typedef struct dvbpsi_pmt_decoder_s
     dvbpsi_pmt_t                  current_pmt;
     dvbpsi_pmt_t *                p_building_pmt;

-} dvbpsi_pmt_decoder_t;
+} __attribute__((__aligned__(128))) dvbpsi_pmt_decoder_t;

 /*****************************************************************************
  * dvbpsi_pmt_sections_gather
diff --git a/src/tables/rst_private.h b/src/tables/rst_private.h
index 2f1664e..c391f76 100644
--- a/src/tables/rst_private.h
+++ b/src/tables/rst_private.h
@@ -42,7 +42,7 @@ typedef struct dvbpsi_rst_decoder_s
     dvbpsi_rst_t                  current_rst;
     dvbpsi_rst_t *                p_building_rst;

-} dvbpsi_rst_decoder_t;
+} __attribute__((__aligned__(128))) dvbpsi_rst_decoder_t;

 /*****************************************************************************
  * dvbpsi_GatherRSTSections
diff --git a/src/tables/sdt_private.h b/src/tables/sdt_private.h
index 1a84dba..b1219fe 100644
--- a/src/tables/sdt_private.h
+++ b/src/tables/sdt_private.h
@@ -43,7 +43,7 @@ typedef struct dvbpsi_sdt_decoder_s
     dvbpsi_sdt_t                  current_sdt;
     dvbpsi_sdt_t *                p_building_sdt;

-} dvbpsi_sdt_decoder_t;
+} __attribute__((__aligned__(128))) dvbpsi_sdt_decoder_t;

 /*****************************************************************************
  * dvbpsi_sdt_sections_gather
diff --git a/src/tables/sis_private.h b/src/tables/sis_private.h
index d539b00..fc69451 100644
--- a/src/tables/sis_private.h
+++ b/src/tables/sis_private.h
@@ -43,7 +43,7 @@ typedef struct dvbpsi_sis_decoder_s
     dvbpsi_sis_t                  current_sis;
     dvbpsi_sis_t                  *p_building_sis;

-} dvbpsi_sis_decoder_t;
+} __attribute__((__aligned__(128))) dvbpsi_sis_decoder_t;

 /*****************************************************************************
  * dvbpsi_sis_sections_gather
diff --git a/src/tables/tot_private.h b/src/tables/tot_private.h
index 86ac502..9a43a8f 100644
--- a/src/tables/tot_private.h
+++ b/src/tables/tot_private.h
@@ -46,7 +46,7 @@ typedef struct dvbpsi_tot_decoder_s
     dvbpsi_tot_t                  current_tot;
     dvbpsi_tot_t                  *p_building_tot;

-} dvbpsi_tot_decoder_t;
+} __attribute__((__aligned__(128))) dvbpsi_tot_decoder_t;


 /*****************************************************************************
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