[cairo] [PATCH 1/2] Fix warning: '*' in boolean context

Discussion:

Uli Schlachter

2017-12-23 13:16:07 UTC

The full message is:

warning: ‘*’ in boolean context, suggest ‘&&’ instead
_cairo_malloc((unsigned) (a) * (unsigned) (size)))
^
note: in definition of macro ‘_cairo_malloc’
((size) ? malloc((unsigned) (size)) : NULL)
^~~~

Signed-off-by: Uli Schlachter <***@znc.in>
---
src/cairo-malloc-private.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/cairo-malloc-private.h b/src/cairo-malloc-private.h
index 1e2c67f8d..570f7cb0e 100644
--- a/src/cairo-malloc-private.h
+++ b/src/cairo-malloc-private.h
@@ -60,7 +60,7 @@
**/

#define _cairo_malloc(size) \
- ((size) ? malloc((unsigned) (size)) : NULL)
+ ((size) > 0 ? malloc((unsigned) (size)) : NULL)

/**
* _cairo_malloc_ab:

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Uli Schlachter

2017-12-23 13:16:08 UTC

Permalink

According to "man setjmp", one possible way to avoid variable clobbering
is to declare them as volatile. Thus, this commit turns the variables
that are changed between setjmp() and longjmp() and whose values are
still needed after setjmp() returned the second time into volatile
variables.

The warning in cairo-bentley-ottmann-rectangular.c is worked around by
not initializing the variable before setjmp(). To be honest, I don't
understand why the compiler warns here at all since the value of update
is clearly not used after setjmp()'s second return.

This commit re-fixes the warnings that were reintroduced in commit
82f40285 which reverted b092b63.

Signed-off-by: Uli Schlachter <***@znc.in>
---
src/cairo-bentley-ottmann-rectangular.c | 4 +++-
src/cairo-png.c | 6 +++---
2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/src/cairo-bentley-ottmann-rectangular.c b/src/cairo-bentley-ottmann-rectangular.c
index 29f902c1a..65f95d797 100644
--- a/src/cairo-bentley-ottmann-rectangular.c
+++ b/src/cairo-bentley-ottmann-rectangular.c
@@ -603,7 +603,7 @@ _cairo_bentley_ottmann_tessellate_rectangular (rectangle_t **rectangles,
sweep_line_t sweep_line;
rectangle_t *rectangle;
cairo_status_t status;
- cairo_bool_t update = FALSE;
+ cairo_bool_t update;

sweep_line_init (&sweep_line,
rectangles, num_rectangles,
@@ -612,6 +612,8 @@ _cairo_bentley_ottmann_tessellate_rectangular (rectangle_t **rectangles,
if ((status = setjmp (sweep_line.unwind)))
return status;

+ update = FALSE;
+
rectangle = rectangle_pop_start (&sweep_line);
do {
if (rectangle->top != sweep_line.current_y) {
diff --git a/src/cairo-png.c b/src/cairo-png.c
index 596b506ab..ab0b9d0c5 100644
--- a/src/cairo-png.c
+++ b/src/cairo-png.c
@@ -544,11 +544,11 @@ stream_read_func (png_structp png, png_bytep data, png_size_t size)
static cairo_surface_t *
read_png (struct png_read_closure_t *png_closure)
{
- cairo_surface_t *surface;
+ cairo_surface_t * volatile surface;
png_struct *png = NULL;
png_info *info;
- png_byte *data = NULL;
- png_byte **row_pointers = NULL;
+ png_byte * volatile data = NULL;
+ png_byte ** volatile row_pointers = NULL;
png_uint_32 png_width, png_height;
int depth, color_type, interlace, stride;
unsigned int i;

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Bryce Harrington

2018-01-05 01:54:37 UTC

Permalink

Post by Uli Schlachter
According to "man setjmp", one possible way to avoid variable clobbering
is to declare them as volatile. Thus, this commit turns the variables
that are changed between setjmp() and longjmp() and whose values are
still needed after setjmp() returned the second time into volatile
variables.
The warning in cairo-bentley-ottmann-rectangular.c is worked around by
not initializing the variable before setjmp(). To be honest, I don't
understand why the compiler warns here at all since the value of update
is clearly not used after setjmp()'s second return.
This commit re-fixes the warnings that were reintroduced in commit
82f40285 which reverted b092b63.

I don't know all the intricacies of volatile and setjmp(), but trust if
it quells the compiler warning it must be good, right?

Post by Uli Schlachter
---
src/cairo-bentley-ottmann-rectangular.c | 4 +++-
src/cairo-png.c | 6 +++---
2 files changed, 6 insertions(+), 4 deletions(-)
diff --git a/src/cairo-bentley-ottmann-rectangular.c b/src/cairo-bentley-ottmann-rectangular.c
index 29f902c1a..65f95d797 100644
--- a/src/cairo-bentley-ottmann-rectangular.c
+++ b/src/cairo-bentley-ottmann-rectangular.c
@@ -603,7 +603,7 @@ _cairo_bentley_ottmann_tessellate_rectangular (rectangle_t **rectangles,
sweep_line_t sweep_line;
rectangle_t *rectangle;
cairo_status_t status;
- cairo_bool_t update = FALSE;
+ cairo_bool_t update;
sweep_line_init (&sweep_line,
rectangles, num_rectangles,
@@ -612,6 +612,8 @@ _cairo_bentley_ottmann_tessellate_rectangular (rectangle_t **rectangles,
if ((status = setjmp (sweep_line.unwind)))
return status;
+ update = FALSE;
+
rectangle = rectangle_pop_start (&sweep_line);
do {
if (rectangle->top != sweep_line.current_y) {
diff --git a/src/cairo-png.c b/src/cairo-png.c
index 596b506ab..ab0b9d0c5 100644
--- a/src/cairo-png.c
+++ b/src/cairo-png.c
@@ -544,11 +544,11 @@ stream_read_func (png_structp png, png_bytep data, png_size_t size)
static cairo_surface_t *
read_png (struct png_read_closure_t *png_closure)
{
- cairo_surface_t *surface;
+ cairo_surface_t * volatile surface;
png_struct *png = NULL;
png_info *info;
- png_byte *data = NULL;
- png_byte **row_pointers = NULL;
+ png_byte * volatile data = NULL;
+ png_byte ** volatile row_pointers = NULL;
png_uint_32 png_width, png_height;
int depth, color_type, interlace, stride;
unsigned int i;
--
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Uli Schlachter

2018-01-13 10:32:36 UTC

Permalink

Post by Bryce Harrington

I don't know all the intricacies of volatile and setjmp(), but trust if
it quells the compiler warning it must be good, right?

By that reasoning, the original patch that I reverted since it caused
endless loops was already good. ;-)

Thanks for taking a look. I just pushed both patches.

Post by Bryce Harrington

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Bryce Harrington

2018-01-05 01:51:49 UTC

Permalink

Post by Uli Schlachter
warning: ‘*’ in boolean context, suggest ‘&&’ instead
_cairo_malloc((unsigned) (a) * (unsigned) (size)))
^
note: in definition of macro ‘_cairo_malloc’
((size) ? malloc((unsigned) (size)) : NULL)
^~~~

Ah, tricky.

Post by Uli Schlachter
---
src/cairo-malloc-private.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/src/cairo-malloc-private.h b/src/cairo-malloc-private.h
index 1e2c67f8d..570f7cb0e 100644
--- a/src/cairo-malloc-private.h
+++ b/src/cairo-malloc-private.h
@@ -60,7 +60,7 @@
**/
#define _cairo_malloc(size) \
- ((size) ? malloc((unsigned) (size)) : NULL)
+ ((size) > 0 ? malloc((unsigned) (size)) : NULL)
/**
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