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loop_invariants.patch
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loop_invariants.patch
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diff --git a/source/core_json.c b/source/core_json.c
index d8694f0..761c44b 100644
--- a/source/core_json.c
+++ b/source/core_json.c
@@ -63,6 +63,21 @@ typedef union
#define isCurlyOpen_( x ) ( ( x ) == '{' )
#define isCurlyClose_( x ) ( ( x ) == '}' )
+/**
+ * Renaming all loop-contract clauses from CBMC for readability.
+ * For more information about loop contracts in CBMC, see
+ * https://diffblue.github.io/cbmc/contracts-user.html.
+ */
+#ifdef CBMC
+ #define loopInvariant(...) __CPROVER_loop_invariant(__VA_ARGS__)
+ #define decreases(...) __CPROVER_decreases(__VA_ARGS__)
+ #define assigns(...) __CPROVER_assigns(__VA_ARGS__)
+#else
+ #define loopInvariant(...)
+ #define decreases(...)
+ #define assigns(...)
+#endif
+
/**
* @brief Advance buffer index beyond whitespace.
*
@@ -79,6 +94,9 @@ static void skipSpace( const char * buf,
coreJSON_ASSERT( ( buf != NULL ) && ( start != NULL ) && ( max > 0U ) );
for( i = *start; i < max; i++ )
+ assigns( i )
+ loopInvariant( *start <= i && i <= max )
+ decreases( max - i )
{
if( !isspace_( buf[ i ] ) )
{
@@ -103,6 +121,13 @@ static size_t countHighBits( uint8_t c )
size_t i = 0;
while( ( n & 0x80U ) != 0U )
+ assigns( i, n )
+ loopInvariant (
+ ( 0U <= i ) && ( i <= 8U )
+ && ( n == ( c & ( 0xFF >> i ) ) << i )
+ && ( ( ( c >> ( 8U - i ) ) + 1U ) == ( 1U << i ) )
+ )
+ decreases( 8U - i )
{
i++;
n = ( n & 0x7FU ) << 1U;
@@ -211,6 +236,13 @@ static bool skipUTF8MultiByte( const char * buf,
/* The bit count is 1 greater than the number of bytes,
* e.g., when j is 2, we skip one more byte. */
for( j = bitCount - 1U; j > 0U; j-- )
+ assigns( j, i, value, c.c )
+ loopInvariant(
+ ( 0 <= j ) && ( j <= bitCount - 1 )
+ && ( *start <= i ) && ( i <= max )
+ && ( ( i == max ) ==> ( j > 0 ) )
+ )
+ decreases( j )
{
i++;
@@ -346,6 +378,12 @@ static bool skipOneHexEscape( const char * buf,
if( ( end < max ) && ( buf[ i ] == '\\' ) && ( buf[ i + 1U ] == 'u' ) )
{
for( i += 2U; i < end; i++ )
+ assigns( value, i )
+ loopInvariant(
+ ( *start + 2U <= i ) && ( i <= end ) &&
+ ( 0U <= value ) && ( value < ( 1U << ( 4U * ( i - ( 2U + *start ) ) ) ) )
+ )
+ decreases( end - i )
{
uint8_t n = hexToInt( buf[ i ] );
@@ -523,6 +561,9 @@ static bool skipString( const char * buf,
i++;
while( i < max )
+ assigns( i )
+ loopInvariant( *start + 1U <= i && i <= max )
+ decreases( max - i )
{
if( buf[ i ] == '"' )
{
@@ -581,6 +622,9 @@ static bool strnEq( const char * a,
coreJSON_ASSERT( ( a != NULL ) && ( b != NULL ) );
for( i = 0; i < n; i++ )
+ assigns( i )
+ loopInvariant( i <= n )
+ decreases( n - i )
{
if( a[ i ] != b[ i ] )
{
@@ -696,6 +740,9 @@ static bool skipDigits( const char * buf,
saveStart = *start;
for( i = *start; i < max; i++ )
+ assigns( value, i )
+ loopInvariant( *start <= i && i <= max )
+ decreases( max - i )
{
if( !isdigit_( buf[ i ] ) )
{
@@ -945,6 +992,9 @@ static void skipArrayScalars( const char * buf,
i = *start;
while( i < max )
+ assigns( i )
+ loopInvariant( *start <= i && i <= max )
+ decreases( max - i )
{
if( skipAnyScalar( buf, &i, max ) != true )
{
@@ -991,6 +1041,13 @@ static bool skipObjectScalars( const char * buf,
i = *start;
while( i < max )
+ assigns( i, *start, comma )
+ loopInvariant(
+ i >= *start
+ && __CPROVER_loop_entry( i ) <= i && i <= max
+ && __CPROVER_loop_entry( *start ) <= *start && *start <= max
+ )
+ decreases( max - i )
{
if( skipString( buf, &i, max ) != true )
{
@@ -1118,6 +1175,14 @@ static JSONStatus_t skipCollection( const char * buf,
i = *start;
while( i < max )
+ assigns( i, depth, c, __CPROVER_object_whole( stack ), ret )
+ loopInvariant(
+ -1 <= depth && depth <= JSON_MAX_DEPTH
+ && *start <= i && i <= max
+ && ( ( ret == JSONSuccess ) ==> i >= *start + 2U )
+ && ( ret == JSONSuccess || ret == JSONPartial || ret == JSONIllegalDocument || ret == JSONMaxDepthExceeded )
+ )
+ decreases( max - i )
{
c = buf[ i ];
i++;
@@ -1407,6 +1472,9 @@ static bool objectSearch( const char * buf,
skipSpace( buf, &i, max );
while( i < max )
+ assigns( i, key, keyLength, value, valueLength )
+ loopInvariant( __CPROVER_loop_entry( i ) <= i && i <= max )
+ decreases( max - i )
{
if( nextKeyValuePair( buf, &i, max, &key, &keyLength,
&value, &valueLength ) != true )
@@ -1474,6 +1542,9 @@ static bool arraySearch( const char * buf,
skipSpace( buf, &i, max );
while( i < max )
+ assigns( i, currentIndex, value, valueLength )
+ loopInvariant( __CPROVER_loop_entry( i ) <= i && i <= max && currentIndex < i )
+ decreases( max - i )
{
if( nextValue( buf, &i, max, &value, &valueLength ) != true )
{
@@ -1539,6 +1610,9 @@ static bool skipQueryPart( const char * buf,
while( ( i < max ) &&
!isSeparator_( buf[ i ] ) &&
!isSquareOpen_( buf[ i ] ) )
+ assigns( i )
+ loopInvariant( i <= max )
+ decreases( max - i )
{
i++;
}
@@ -1585,6 +1659,17 @@ static JSONStatus_t multiSearch( const char * buf,
coreJSON_ASSERT( ( max > 0U ) && ( queryLength > 0U ) );
while( i < queryLength )
+ assigns( i, start, queryStart, value, length )
+ loopInvariant(
+ 0U <= start && start < max
+ && 0U < length && length <= max
+ && start + length <= max
+ && ( ( i == queryLength && ret == JSONSuccess && buf[ start ] == '"' ) ==> length >= 2U )
+ && 0U <= value && value < max
+ && 0U <= i && i <= queryLength
+ && 0U <= queryStart && queryStart <= queryLength
+ )
+ decreases( queryLength - i )
{
bool found = false;