[PATCH mmc-utils] fix GCC7 build by refactoring trimming routines

[PATCH mmc-utils] fix GCC7 build by refactoring trimming routines

[Wolfram Sang]

I got a compile error with GCC7. When trimming white spaces from strings
lsmmc uses strncpy with overlapping memory areas. This is not allowed.
In addition, the implementation was not efficient with calling strlen
and strncpy once per iteration. Refactor the code to be valid and more
effective.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
---
 lsmmc.c | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/lsmmc.c b/lsmmc.c
index c4faa00..9737b37 100644
--- a/lsmmc.c
+++ b/lsmmc.c
@@ -316,8 +316,9 @@ int parse_ids(struct config *config)
 /* MMC/SD file parsing functions */
 char *read_file(char *name)
 {
-	char *preparsed;
 	char line[4096];
+	char *preparsed, *start = line;
+	int len;
 	FILE *f;
 
 	f = fopen(name, "r");
@@ -348,12 +349,17 @@ char *read_file(char *name)
 	}
 
 	line[sizeof(line) - 1] = '\0';
+	len = strlen(line);
 
-	while (isspace(line[strlen(line) - 1]))
-		line[strlen(line) - 1] = '\0';
+	while (len > 0 && isspace(line[len - 1]))
+		len--;
 
-	while (isspace(line[0]))
-		strncpy(&line[0], &line[1], sizeof(line));
+	while (len > 0 && isspace(*start)) {
+		start++;
+		len--;
+	}
+	memmove(line, start, len);
+	line[len] = '\0';
 
 	return strdup(line);
 }
-- 
2.11.0

RE: [PATCH mmc-utils] fix GCC7 build by refactoring trimming routines

[Avri Altman]

Hi,

> 
> I got a compile error with GCC7. When trimming white spaces from strings
> lsmmc uses strncpy with overlapping memory areas. This is not allowed.
> In addition, the implementation was not efficient with calling strlen
> and strncpy once per iteration. Refactor the code to be valid and more
> effective.
> 
> Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
> ---
>  lsmmc.c | 16 +++++++++++-----
>  1 file changed, 11 insertions(+), 5 deletions(-)
> 
> diff --git a/lsmmc.c b/lsmmc.c
> index c4faa00..9737b37 100644
> --- a/lsmmc.c
> +++ b/lsmmc.c
> @@ -316,8 +316,9 @@ int parse_ids(struct config *config)
>  /* MMC/SD file parsing functions */
>  char *read_file(char *name)
>  {

See Uwe's note - https://www.spinics.net/lists/linux-mmc/msg51882.html

Cheers,
Avri

Re: [PATCH mmc-utils] fix GCC7 build by refactoring trimming routines

[Wolfram Sang]

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Hi Avri, hi Chris,

> > I got a compile error with GCC7. When trimming white spaces from strings
> > lsmmc uses strncpy with overlapping memory areas. This is not allowed.
> > In addition, the implementation was not efficient with calling strlen
> > and strncpy once per iteration. Refactor the code to be valid and more
> > effective.
> > 
> > Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
> > ---
> >  lsmmc.c | 16 +++++++++++-----
> >  1 file changed, 11 insertions(+), 5 deletions(-)
> > 
> > diff --git a/lsmmc.c b/lsmmc.c
> > index c4faa00..9737b37 100644
> > --- a/lsmmc.c
> > +++ b/lsmmc.c
> > @@ -316,8 +316,9 @@ int parse_ids(struct config *config)
> >  /* MMC/SD file parsing functions */
> >  char *read_file(char *name)
> >  {
> 
> See Uwe's note - https://www.spinics.net/lists/linux-mmc/msg51882.html

Thanks for the pointer. Chris, how do you feel with maintaining
mmc-utils? Would you maybe be willing to share maintenance with someone?

Happy hacking,

   Wolfram


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Re: [PATCH mmc-utils] fix GCC7 build by refactoring trimming routines

[Chris Ball]

Hi everyone, I'm very sorry for the delay in responding to these patches
and the duplicated effort it caused.

On Mon, Dec 03, 2018 at 03:24:42PM +0100, Wolfram Sang wrote:
> Hi Avri, hi Chris,
> 
> > > I got a compile error with GCC7. When trimming white spaces from strings
> > > lsmmc uses strncpy with overlapping memory areas. This is not allowed.
> > > In addition, the implementation was not efficient with calling strlen
> > > and strncpy once per iteration. Refactor the code to be valid and more
> > > effective.
> > > 
> > > Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>

Thanks, I've applied this fix of Wolfram's to mmc-utils master.

> Thanks for the pointer. Chris, how do you feel with maintaining
> mmc-utils? Would you maybe be willing to share maintenance with someone?

Yep, that'd make sense.

-- 
Chris Ball   <http://printf.net/>